diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
index b65a5fbd5d6..4346c16007a 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
@@ -292,13 +292,11 @@ public class DefaultGenerator implements Generator {
         // set OpenAPI to make these available to all methods
         config.setOpenAPI(openAPI);
 
-        if (!config.additionalProperties().containsKey("generatorVersion")) {
-            config.additionalProperties().put("generatorVersion", ImplementationVersion.read());
-        }
-        config.additionalProperties().put("generatedDate", ZonedDateTime.now().toString());
-        config.additionalProperties().put("generatedYear", String.valueOf(ZonedDateTime.now().getYear()));
-        config.additionalProperties().put("generatorClass", config.getClass().getName());
-        config.additionalProperties().put("inputSpec", config.getInputSpec());
+        config.additionalProperties().putIfAbsent("generatorVersion", ImplementationVersion.read());
+        config.additionalProperties().putIfAbsent("generatedDate", ZonedDateTime.now().toString());
+        config.additionalProperties().putIfAbsent("generatedYear", String.valueOf(ZonedDateTime.now().getYear()));
+        config.additionalProperties().putIfAbsent("generatorClass", config.getClass().getName());
+        config.additionalProperties().putIfAbsent("inputSpec", config.getInputSpec());
 
         if (openAPI.getExtensions() != null) {
             config.vendorExtensions().putAll(openAPI.getExtensions());
@@ -322,59 +320,59 @@ public class DefaultGenerator implements Generator {
             return;
         }
         if (info.getTitle() != null) {
-            config.additionalProperties().put("appName", config.escapeText(info.getTitle()));
+            config.additionalProperties().putIfAbsent("appName", config.escapeText(info.getTitle()));
         }
         if (info.getVersion() != null) {
-            config.additionalProperties().put("appVersion", config.escapeText(info.getVersion()));
+            config.additionalProperties().putIfAbsent("appVersion", config.escapeText(info.getVersion()));
         } else {
             LOGGER.error("Missing required field info version. Default appVersion set to 1.0.0");
-            config.additionalProperties().put("appVersion", "1.0.0");
+            config.additionalProperties().putIfAbsent("appVersion", "1.0.0");
         }
 
         if (StringUtils.isEmpty(info.getDescription())) {
             // set a default description if none if provided
-            config.additionalProperties().put("appDescription",
+            config.additionalProperties().putIfAbsent("appDescription",
                     "No description provided (generated by Openapi Generator https://github.com/openapitools/openapi-generator)");
-            config.additionalProperties().put("appDescriptionWithNewLines", config.additionalProperties().get("appDescription"));
-            config.additionalProperties().put("unescapedAppDescription", "No description provided (generated by Openapi Generator https://github.com/openapitools/openapi-generator)");
+            config.additionalProperties().putIfAbsent("appDescriptionWithNewLines", config.additionalProperties().get("appDescription"));
+            config.additionalProperties().putIfAbsent("unescapedAppDescription", "No description provided (generated by Openapi Generator https://github.com/openapitools/openapi-generator)");
         } else {
-            config.additionalProperties().put("appDescription", config.escapeText(info.getDescription()));
-            config.additionalProperties().put("appDescriptionWithNewLines", config.escapeTextWhileAllowingNewLines(info.getDescription()));
-            config.additionalProperties().put("unescapedAppDescription", info.getDescription());
+            config.additionalProperties().putIfAbsent("appDescription", config.escapeText(info.getDescription()));
+            config.additionalProperties().putIfAbsent("appDescriptionWithNewLines", config.escapeTextWhileAllowingNewLines(info.getDescription()));
+            config.additionalProperties().putIfAbsent("unescapedAppDescription", info.getDescription());
         }
 
         if (info.getContact() != null) {
             Contact contact = info.getContact();
             if (contact.getEmail() != null) {
-                config.additionalProperties().put("infoEmail", config.escapeText(contact.getEmail()));
+                config.additionalProperties().putIfAbsent("infoEmail", config.escapeText(contact.getEmail()));
             }
             if (contact.getName() != null) {
-                config.additionalProperties().put("infoName", config.escapeText(contact.getName()));
+                config.additionalProperties().putIfAbsent("infoName", config.escapeText(contact.getName()));
             }
             if (contact.getUrl() != null) {
-                config.additionalProperties().put("infoUrl", config.escapeText(contact.getUrl()));
+                config.additionalProperties().putIfAbsent("infoUrl", config.escapeText(contact.getUrl()));
             }
         }
 
         if (info.getLicense() != null) {
             License license = info.getLicense();
             if (license.getName() != null) {
-                config.additionalProperties().put("licenseInfo", config.escapeText(license.getName()));
+                config.additionalProperties().putIfAbsent("licenseInfo", config.escapeText(license.getName()));
             }
             if (license.getUrl() != null) {
-                config.additionalProperties().put("licenseUrl", config.escapeText(license.getUrl()));
+                config.additionalProperties().putIfAbsent("licenseUrl", config.escapeText(license.getUrl()));
             }
         }
 
         if (info.getVersion() != null) {
-            config.additionalProperties().put("version", config.escapeText(info.getVersion()));
+            config.additionalProperties().putIfAbsent("version", config.escapeText(info.getVersion()));
         } else {
             LOGGER.error("Missing required field info version. Default version set to 1.0.0");
-            config.additionalProperties().put("version", "1.0.0");
+            config.additionalProperties().putIfAbsent("version", "1.0.0");
         }
 
         if (info.getTermsOfService() != null) {
-            config.additionalProperties().put("termsOfService", config.escapeText(info.getTermsOfService()));
+            config.additionalProperties().putIfAbsent("termsOfService", config.escapeText(info.getTermsOfService()));
         }
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/asciidoc/AsciidocGeneratorTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/asciidoc/AsciidocGeneratorTest.java
index c5f01e4b74d..c2762fd2bfd 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/asciidoc/AsciidocGeneratorTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/asciidoc/AsciidocGeneratorTest.java
@@ -72,6 +72,7 @@ public class AsciidocGeneratorTest {
                 markupFileGenerated = true;
                 String markupContent = FileUtils.readFileToString(file, StandardCharsets.UTF_8);
                 // check on some basic asciidoc markup content
+                Assert.assertEquals("", markupContent);
                 Assert.assertTrue(markupContent.contains("= ping test"),
                         "expected = header in: " + markupContent.substring(0, 50));
                 Assert.assertTrue(markupContent.contains(":toc: "),