diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaCXFExtServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaCXFExtServerCodegen.java
index beb9aae85ff..bb727af8f2b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaCXFExtServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaCXFExtServerCodegen.java
@@ -623,14 +623,16 @@ public class JavaCXFExtServerCodegen extends JavaCXFServerCodegen implements CXF
             // the OpenAPI 2.0/3.0 specs, which mandates the ISO-8601 full-date or date-time formats. Accordingly, date
             // and date-time fields are annotated with @JsonFormat to specify the appropriate ISO format.
             if (loadTestDataFromFile) {
-                Date randomDate = new Date(randomDateLong);
-                switch (var.dataFormat) {
-                    case "date":
-                        var.addTestData(ISO8601_DATE_FORMAT.get().format(randomDate));
-                        break;
-                    case "date-time":
-                        var.addTestData(ISO8601_DATETIME_FORMAT.get().format(randomDate));
-                        break;
+                if (var != null) {
+                    Date randomDate = new Date(randomDateLong);
+                    switch (var.dataFormat) {
+                        case "date":
+                            var.addTestData(ISO8601_DATE_FORMAT.get().format(randomDate));
+                            break;
+                        case "date-time":
+                            var.addTestData(ISO8601_DATETIME_FORMAT.get().format(randomDate));
+                            break;
+                    }
                 }
             } else {
                 buffer.append("new Date(").append(randomDateLong).append(')');
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java
index caaef6ce280..1241e9f4e62 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java
@@ -172,18 +172,20 @@ public class ModelUtils {
         childrenMap = tmpChildrenMap;
         List<String> unusedSchemas = new ArrayList<String>();
 
-        Map<String, Schema> schemas = getSchemas(openAPI);
-        unusedSchemas.addAll(schemas.keySet());
+        if (openAPI != null) {
+            Map<String, Schema> schemas = getSchemas(openAPI);
+            unusedSchemas.addAll(schemas.keySet());
 
-        visitOpenAPI(openAPI, (s, t) -> {
-            if (s.get$ref() != null) {
-                String ref = getSimpleRef(s.get$ref());
-                unusedSchemas.remove(ref);
-                if (childrenMap.containsKey(ref)) {
-                    unusedSchemas.removeAll(childrenMap.get(ref));
+            visitOpenAPI(openAPI, (s, t) -> {
+                if (s.get$ref() != null) {
+                    String ref = getSimpleRef(s.get$ref());
+                    unusedSchemas.remove(ref);
+                    if (childrenMap.containsKey(ref)) {
+                        unusedSchemas.removeAll(childrenMap.get(ref));
+                    }
                 }
-            }
-        });
+            });
+        }
         return unusedSchemas;
     }
 
diff --git a/samples/openapi3/client/features/dynamic-servers/ruby/lib/dynamic_servers/api/usage_api.rb b/samples/openapi3/client/features/dynamic-servers/ruby/lib/dynamic_servers/api/usage_api.rb
index 0c2af6222dd..80470703161 100644
--- a/samples/openapi3/client/features/dynamic-servers/ruby/lib/dynamic_servers/api/usage_api.rb
+++ b/samples/openapi3/client/features/dynamic-servers/ruby/lib/dynamic_servers/api/usage_api.rb
@@ -51,13 +51,13 @@ module DynamicServers
       form_params = opts[:form_params] || {}
 
       # http body (model)
-      post_body = opts[:body] 
+      post_body = opts[:debug_body]
 
       # return_type
-      return_type = opts[:return_type] || 'Object' 
+      return_type = opts[:debug_return_type] || 'Object'
 
       # auth_names
-      auth_names = opts[:auth_names] || []
+      auth_names = opts[:debug_auth_names] || []
 
       new_options = opts.merge(
         :operation => :"UsageApi.custom_server",
@@ -108,13 +108,13 @@ module DynamicServers
       form_params = opts[:form_params] || {}
 
       # http body (model)
-      post_body = opts[:body] 
+      post_body = opts[:debug_body]
 
       # return_type
-      return_type = opts[:return_type] || 'Object' 
+      return_type = opts[:debug_return_type] || 'Object'
 
       # auth_names
-      auth_names = opts[:auth_names] || []
+      auth_names = opts[:debug_auth_names] || []
 
       new_options = opts.merge(
         :operation => :"UsageApi.default_server",