diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RClientCodegen.java
index a599bedd699..8d6b8d15916 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RClientCodegen.java
@@ -288,7 +288,7 @@ public class RClientCodegen extends DefaultCodegen implements CodegenConfig {
         supportingFiles.add(new SupportingFile("gitignore.mustache", "", ".gitignore"));
         supportingFiles.add(new SupportingFile("description.mustache", "", "DESCRIPTION"));
         supportingFiles.add(new SupportingFile("Rbuildignore.mustache", "", ".Rbuildignore"));
-        supportingFiles.add(new SupportingFile(".travis.yml", "", ".travis.yml"));
+        supportingFiles.add(new SupportingFile(".travis.yml.mustache", "", ".travis.yml"));
         supportingFiles.add(new SupportingFile("ApiResponse.mustache", File.separator + "R", "api_response.R"));
         supportingFiles.add(new SupportingFile("api_client.mustache", File.separator + "R", "api_client.R"));
         supportingFiles.add(new SupportingFile("NAMESPACE.mustache", "", "NAMESPACE"));
@@ -320,6 +320,16 @@ public class RClientCodegen extends DefaultCodegen implements CodegenConfig {
             }
         });
 
+        // add lambda for mustache templates to escape %
+        additionalProperties.put("lambdaRdocEscape", new Mustache.Lambda() {
+            @Override
+            public void execute(Template.Fragment fragment, Writer writer) throws IOException {
+                String content = fragment.execute();
+                content = content.trim().replace("%", "\\%");
+                writer.write(content);
+            }
+        });
+
     }
 
     @Override
diff --git a/modules/openapi-generator/src/main/resources/r/.travis.yml b/modules/openapi-generator/src/main/resources/r/.travis.yml.mustache
similarity index 87%
rename from modules/openapi-generator/src/main/resources/r/.travis.yml
rename to modules/openapi-generator/src/main/resources/r/.travis.yml.mustache
index b96a0ef5a85..a14eb1abdd1 100644
--- a/modules/openapi-generator/src/main/resources/r/.travis.yml
+++ b/modules/openapi-generator/src/main/resources/r/.travis.yml.mustache
@@ -5,7 +5,12 @@ cache:
   - /home/travis/R/Library
 r_packages:
 - jsonlite
+{{^isHttr2}}
 - httr
+{{/isHttr2}}
+{{#isHttr2}}
+- httr2
+{{/isHttr2}}
 - testthat
 # uncomment below to install deps with devtools
 #install:
diff --git a/modules/openapi-generator/src/main/resources/r/api.mustache b/modules/openapi-generator/src/main/resources/r/api.mustache
index 1b93f6119c2..bf0551def51 100644
--- a/modules/openapi-generator/src/main/resources/r/api.mustache
+++ b/modules/openapi-generator/src/main/resources/r/api.mustache
@@ -10,9 +10,9 @@
 {{! Adding the below changes for generating documentation for the api methods. }}
 #' \describe{
 {{#operation}}
-#' \strong{ {{operationId}} } \emph{ {{summary}} }
+#' \strong{ {{operationId}} } \emph{ {{#lambdaRdocEscape}}{{summary}}{{/lambdaRdocEscape}} }
 {{#notes}}
-#' {{{.}}}
+#' {{#lambdaRdocEscape}}{{{.}}}{{/lambdaRdocEscape}}
 {{/notes}}
 #'
 #' \itemize{
@@ -573,4 +573,4 @@
     {{/operation}}
   )
 )
-{{/operations}}
\ No newline at end of file
+{{/operations}}
diff --git a/modules/openapi-generator/src/main/resources/r/modelGeneric.mustache b/modules/openapi-generator/src/main/resources/r/modelGeneric.mustache
index d8290e4aab9..3897333fe71 100644
--- a/modules/openapi-generator/src/main/resources/r/modelGeneric.mustache
+++ b/modules/openapi-generator/src/main/resources/r/modelGeneric.mustache
@@ -23,10 +23,10 @@
     #' Initialize a new {{{classname}}} class.
     #'
     {{#requiredVars}}
-    #' @param {{name}} {{{description}}}{{^description}}{{{name}}}{{/description}}
+    #' @param {{name}} {{#lambdaRdocEscape}}{{{description}}}{{/lambdaRdocEscape}}{{^description}}{{{name}}}{{/description}}
     {{/requiredVars}}
     {{#optionalVars}}
-    #' @param {{name}} {{{description}}}{{^description}}{{{name}}}{{/description}}{{#defaultValue}}. Default to {{{.}}}.{{/defaultValue}}
+    #' @param {{name}} {{#lambdaRdocEscape}}{{{description}}}{{/lambdaRdocEscape}}{{^description}}{{{name}}}{{/description}}{{#defaultValue}}. Default to {{{.}}}.{{/defaultValue}}
     {{/optionalVars}}
     #' @param ... Other optional arguments.
     #' @export
@@ -428,7 +428,7 @@
       {{#required}}
       # check if the required `{{{name}}}` is null
       if (is.null(self$`{{{name}}}`)) {
-        invalid_fields["{{{name}}}"] = "Non-nullable required field `{{{name}}}` cannot be null."
+        invalid_fields["{{{name}}}"] <- "Non-nullable required field `{{{name}}}` cannot be null."
       }
 
       {{/required}}
@@ -436,37 +436,37 @@
       {{#hasValidation}}
       {{#maxLength}}
       if (nchar(self$`{{{name}}}`) > {{maxLength}}) {
-        invalid_fields["{{{name}}}"] = "Invalid length for `{{{name}}}`, must be smaller than or equal to {{maxLength}}."
+        invalid_fields["{{{name}}}"] <- "Invalid length for `{{{name}}}`, must be smaller than or equal to {{maxLength}}."
       }
       {{/maxLength}}
       {{#minLength}}
       if (nchar(self$`{{{name}}}`) < {{minLength}}) {
-        invalid_fields["{{{name}}}"] = "Invalid length for `{{{name}}}`, must be bigger than or equal to {{minLength}}."
+        invalid_fields["{{{name}}}"] <- "Invalid length for `{{{name}}}`, must be bigger than or equal to {{minLength}}."
       }
       {{/minLength}}
       {{#maximum}}
       if (self$`{{{name}}}` >{{#exclusiveMaximum}}={{/exclusiveMaximum}} {{maximum}}) {
-        invalid_fields["{{{name}}}"] = "Invalid value for `{{{name}}}`, must be smaller than {{^exclusiveMaximum}}or equal to {{/exclusiveMaximum}}{{maximum}}."
+        invalid_fields["{{{name}}}"] <- "Invalid value for `{{{name}}}`, must be smaller than {{^exclusiveMaximum}}or equal to {{/exclusiveMaximum}}{{maximum}}."
       }
       {{/maximum}}
       {{#minimum}}
       if (self$`{{{name}}}` <{{#exclusiveMinimum}}={{/exclusiveMinimum}} {{minimum}}) {
-        invalid_fields["{{{name}}}"] = "Invalid value for `{{{name}}}`, must be bigger than {{^exclusiveMinimum}}or equal to {{/exclusiveMinimum}}{{minimum}}."
+        invalid_fields["{{{name}}}"] <- "Invalid value for `{{{name}}}`, must be bigger than {{^exclusiveMinimum}}or equal to {{/exclusiveMinimum}}{{minimum}}."
       }
       {{/minimum}}
       {{#pattern}}
       if (!str_detect(self$`{{{name}}}`, "{{{pattern}}}")) {
-        invalid_fields["{{{name}}}"] = "Invalid value for `{{{name}}}`, must conform to the pattern {{{pattern}}}."
+        invalid_fields["{{{name}}}"] <- "Invalid value for `{{{name}}}`, must conform to the pattern {{{pattern}}}."
       }
       {{/pattern}}
       {{#maxItems}}
       if (length(self$`{{{name}}}`) > {{maxItems}}) {
-        invalid_fields["{{{name}}}"] = "Invalid length for `{{{name}}}`, number of items must be less than or equal to {{maxItems}}."
+        invalid_fields["{{{name}}}"] <- "Invalid length for `{{{name}}}`, number of items must be less than or equal to {{maxItems}}."
       }
       {{/maxItems}}
       {{#minItems}}
       if (length(self$`{{{name}}}`) < {{minItems}}) {
-        invalid_fields["{{{name}}}"] = "Invalid length for `{{{param}}}`, number of items must be greater than or equal to {{minItems}}."
+        invalid_fields["{{{name}}}"] <- "Invalid length for `{{{param}}}`, number of items must be greater than or equal to {{minItems}}."
       }
       {{/minItems}}
 
diff --git a/samples/client/petstore/R-httr2-wrapper/.travis.yml b/samples/client/petstore/R-httr2-wrapper/.travis.yml
index b96a0ef5a85..60f31f31078 100644
--- a/samples/client/petstore/R-httr2-wrapper/.travis.yml
+++ b/samples/client/petstore/R-httr2-wrapper/.travis.yml
@@ -5,7 +5,7 @@ cache:
   - /home/travis/R/Library
 r_packages:
 - jsonlite
-- httr
+- httr2
 - testthat
 # uncomment below to install deps with devtools
 #install:
diff --git a/samples/client/petstore/R-httr2-wrapper/R/animal.R b/samples/client/petstore/R-httr2-wrapper/R/animal.R
index 296e59eee89..97d3f146df5 100644
--- a/samples/client/petstore/R-httr2-wrapper/R/animal.R
+++ b/samples/client/petstore/R-httr2-wrapper/R/animal.R
@@ -173,7 +173,7 @@ Animal <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2-wrapper/R/basque_pig.R b/samples/client/petstore/R-httr2-wrapper/R/basque_pig.R
index 13c67075a2d..4cf229f8f7e 100644
--- a/samples/client/petstore/R-httr2-wrapper/R/basque_pig.R
+++ b/samples/client/petstore/R-httr2-wrapper/R/basque_pig.R
@@ -184,12 +184,12 @@ BasquePig <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       # check if the required `color` is null
       if (is.null(self$`color`)) {
-        invalid_fields["color"] = "Non-nullable required field `color` cannot be null."
+        invalid_fields["color"] <- "Non-nullable required field `color` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2-wrapper/R/cat.R b/samples/client/petstore/R-httr2-wrapper/R/cat.R
index 9e74249b400..4d94ee18d76 100644
--- a/samples/client/petstore/R-httr2-wrapper/R/cat.R
+++ b/samples/client/petstore/R-httr2-wrapper/R/cat.R
@@ -197,7 +197,7 @@ Cat <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2-wrapper/R/category.R b/samples/client/petstore/R-httr2-wrapper/R/category.R
index 88470c001ba..78564e356c9 100644
--- a/samples/client/petstore/R-httr2-wrapper/R/category.R
+++ b/samples/client/petstore/R-httr2-wrapper/R/category.R
@@ -165,7 +165,7 @@ Category <- R6::R6Class(
     getInvalidFields = function() {
       invalid_fields <- list()
       if (!str_detect(self$`name`, "^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$")) {
-        invalid_fields["name"] = "Invalid value for `name`, must conform to the pattern ^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$."
+        invalid_fields["name"] <- "Invalid value for `name`, must conform to the pattern ^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2-wrapper/R/danish_pig.R b/samples/client/petstore/R-httr2-wrapper/R/danish_pig.R
index 6cde3c461d7..320ea4ebda2 100644
--- a/samples/client/petstore/R-httr2-wrapper/R/danish_pig.R
+++ b/samples/client/petstore/R-httr2-wrapper/R/danish_pig.R
@@ -184,12 +184,12 @@ DanishPig <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       # check if the required `size` is null
       if (is.null(self$`size`)) {
-        invalid_fields["size"] = "Non-nullable required field `size` cannot be null."
+        invalid_fields["size"] <- "Non-nullable required field `size` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2-wrapper/R/dog.R b/samples/client/petstore/R-httr2-wrapper/R/dog.R
index f89cecf6523..85674525e6a 100644
--- a/samples/client/petstore/R-httr2-wrapper/R/dog.R
+++ b/samples/client/petstore/R-httr2-wrapper/R/dog.R
@@ -197,7 +197,7 @@ Dog <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2-wrapper/R/pet.R b/samples/client/petstore/R-httr2-wrapper/R/pet.R
index 6d71b14dec2..b336816c598 100644
--- a/samples/client/petstore/R-httr2-wrapper/R/pet.R
+++ b/samples/client/petstore/R-httr2-wrapper/R/pet.R
@@ -281,12 +281,12 @@ Pet <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `name` is null
       if (is.null(self$`name`)) {
-        invalid_fields["name"] = "Non-nullable required field `name` cannot be null."
+        invalid_fields["name"] <- "Non-nullable required field `name` cannot be null."
       }
 
       # check if the required `photoUrls` is null
       if (is.null(self$`photoUrls`)) {
-        invalid_fields["photoUrls"] = "Non-nullable required field `photoUrls` cannot be null."
+        invalid_fields["photoUrls"] <- "Non-nullable required field `photoUrls` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2/.travis.yml b/samples/client/petstore/R-httr2/.travis.yml
index b96a0ef5a85..60f31f31078 100644
--- a/samples/client/petstore/R-httr2/.travis.yml
+++ b/samples/client/petstore/R-httr2/.travis.yml
@@ -5,7 +5,7 @@ cache:
   - /home/travis/R/Library
 r_packages:
 - jsonlite
-- httr
+- httr2
 - testthat
 # uncomment below to install deps with devtools
 #install:
diff --git a/samples/client/petstore/R-httr2/R/animal.R b/samples/client/petstore/R-httr2/R/animal.R
index 296e59eee89..97d3f146df5 100644
--- a/samples/client/petstore/R-httr2/R/animal.R
+++ b/samples/client/petstore/R-httr2/R/animal.R
@@ -173,7 +173,7 @@ Animal <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2/R/basque_pig.R b/samples/client/petstore/R-httr2/R/basque_pig.R
index 13c67075a2d..4cf229f8f7e 100644
--- a/samples/client/petstore/R-httr2/R/basque_pig.R
+++ b/samples/client/petstore/R-httr2/R/basque_pig.R
@@ -184,12 +184,12 @@ BasquePig <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       # check if the required `color` is null
       if (is.null(self$`color`)) {
-        invalid_fields["color"] = "Non-nullable required field `color` cannot be null."
+        invalid_fields["color"] <- "Non-nullable required field `color` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2/R/cat.R b/samples/client/petstore/R-httr2/R/cat.R
index 9e74249b400..4d94ee18d76 100644
--- a/samples/client/petstore/R-httr2/R/cat.R
+++ b/samples/client/petstore/R-httr2/R/cat.R
@@ -197,7 +197,7 @@ Cat <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2/R/category.R b/samples/client/petstore/R-httr2/R/category.R
index 88470c001ba..78564e356c9 100644
--- a/samples/client/petstore/R-httr2/R/category.R
+++ b/samples/client/petstore/R-httr2/R/category.R
@@ -165,7 +165,7 @@ Category <- R6::R6Class(
     getInvalidFields = function() {
       invalid_fields <- list()
       if (!str_detect(self$`name`, "^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$")) {
-        invalid_fields["name"] = "Invalid value for `name`, must conform to the pattern ^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$."
+        invalid_fields["name"] <- "Invalid value for `name`, must conform to the pattern ^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2/R/danish_pig.R b/samples/client/petstore/R-httr2/R/danish_pig.R
index 6cde3c461d7..320ea4ebda2 100644
--- a/samples/client/petstore/R-httr2/R/danish_pig.R
+++ b/samples/client/petstore/R-httr2/R/danish_pig.R
@@ -184,12 +184,12 @@ DanishPig <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       # check if the required `size` is null
       if (is.null(self$`size`)) {
-        invalid_fields["size"] = "Non-nullable required field `size` cannot be null."
+        invalid_fields["size"] <- "Non-nullable required field `size` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2/R/dog.R b/samples/client/petstore/R-httr2/R/dog.R
index f89cecf6523..85674525e6a 100644
--- a/samples/client/petstore/R-httr2/R/dog.R
+++ b/samples/client/petstore/R-httr2/R/dog.R
@@ -197,7 +197,7 @@ Dog <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R-httr2/R/pet.R b/samples/client/petstore/R-httr2/R/pet.R
index 6d71b14dec2..b336816c598 100644
--- a/samples/client/petstore/R-httr2/R/pet.R
+++ b/samples/client/petstore/R-httr2/R/pet.R
@@ -281,12 +281,12 @@ Pet <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `name` is null
       if (is.null(self$`name`)) {
-        invalid_fields["name"] = "Non-nullable required field `name` cannot be null."
+        invalid_fields["name"] <- "Non-nullable required field `name` cannot be null."
       }
 
       # check if the required `photoUrls` is null
       if (is.null(self$`photoUrls`)) {
-        invalid_fields["photoUrls"] = "Non-nullable required field `photoUrls` cannot be null."
+        invalid_fields["photoUrls"] <- "Non-nullable required field `photoUrls` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R/R/animal.R b/samples/client/petstore/R/R/animal.R
index 296e59eee89..97d3f146df5 100644
--- a/samples/client/petstore/R/R/animal.R
+++ b/samples/client/petstore/R/R/animal.R
@@ -173,7 +173,7 @@ Animal <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R/R/basque_pig.R b/samples/client/petstore/R/R/basque_pig.R
index 13c67075a2d..4cf229f8f7e 100644
--- a/samples/client/petstore/R/R/basque_pig.R
+++ b/samples/client/petstore/R/R/basque_pig.R
@@ -184,12 +184,12 @@ BasquePig <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       # check if the required `color` is null
       if (is.null(self$`color`)) {
-        invalid_fields["color"] = "Non-nullable required field `color` cannot be null."
+        invalid_fields["color"] <- "Non-nullable required field `color` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R/R/cat.R b/samples/client/petstore/R/R/cat.R
index 9e74249b400..4d94ee18d76 100644
--- a/samples/client/petstore/R/R/cat.R
+++ b/samples/client/petstore/R/R/cat.R
@@ -197,7 +197,7 @@ Cat <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R/R/category.R b/samples/client/petstore/R/R/category.R
index 88470c001ba..78564e356c9 100644
--- a/samples/client/petstore/R/R/category.R
+++ b/samples/client/petstore/R/R/category.R
@@ -165,7 +165,7 @@ Category <- R6::R6Class(
     getInvalidFields = function() {
       invalid_fields <- list()
       if (!str_detect(self$`name`, "^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$")) {
-        invalid_fields["name"] = "Invalid value for `name`, must conform to the pattern ^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$."
+        invalid_fields["name"] <- "Invalid value for `name`, must conform to the pattern ^[a-zA-Z0-9]+[a-zA-Z0-9\\.\\-_]*[a-zA-Z0-9]+$."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R/R/danish_pig.R b/samples/client/petstore/R/R/danish_pig.R
index 6cde3c461d7..320ea4ebda2 100644
--- a/samples/client/petstore/R/R/danish_pig.R
+++ b/samples/client/petstore/R/R/danish_pig.R
@@ -184,12 +184,12 @@ DanishPig <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       # check if the required `size` is null
       if (is.null(self$`size`)) {
-        invalid_fields["size"] = "Non-nullable required field `size` cannot be null."
+        invalid_fields["size"] <- "Non-nullable required field `size` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R/R/dog.R b/samples/client/petstore/R/R/dog.R
index f89cecf6523..85674525e6a 100644
--- a/samples/client/petstore/R/R/dog.R
+++ b/samples/client/petstore/R/R/dog.R
@@ -197,7 +197,7 @@ Dog <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `className` is null
       if (is.null(self$`className`)) {
-        invalid_fields["className"] = "Non-nullable required field `className` cannot be null."
+        invalid_fields["className"] <- "Non-nullable required field `className` cannot be null."
       }
 
       invalid_fields
diff --git a/samples/client/petstore/R/R/pet.R b/samples/client/petstore/R/R/pet.R
index 6d71b14dec2..b336816c598 100644
--- a/samples/client/petstore/R/R/pet.R
+++ b/samples/client/petstore/R/R/pet.R
@@ -281,12 +281,12 @@ Pet <- R6::R6Class(
       invalid_fields <- list()
       # check if the required `name` is null
       if (is.null(self$`name`)) {
-        invalid_fields["name"] = "Non-nullable required field `name` cannot be null."
+        invalid_fields["name"] <- "Non-nullable required field `name` cannot be null."
       }
 
       # check if the required `photoUrls` is null
       if (is.null(self$`photoUrls`)) {
-        invalid_fields["photoUrls"] = "Non-nullable required field `photoUrls` cannot be null."
+        invalid_fields["photoUrls"] <- "Non-nullable required field `photoUrls` cannot be null."
       }
 
       invalid_fields