diff --git a/modules/swagger-codegen-maven-plugin/src/main/java/io/swagger/codegen/plugin/CodeGenMojo.java b/modules/swagger-codegen-maven-plugin/src/main/java/io/swagger/codegen/plugin/CodeGenMojo.java
index 58fbeda5943..446acc9849e 100644
--- a/modules/swagger-codegen-maven-plugin/src/main/java/io/swagger/codegen/plugin/CodeGenMojo.java
+++ b/modules/swagger-codegen-maven-plugin/src/main/java/io/swagger/codegen/plugin/CodeGenMojo.java
@@ -2,12 +2,12 @@
 
 /*
  * Copyright 2001-2005 The Apache Software Foundation.
- * 
+ *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
- * 
+ *
  * http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software distributed under the License
  * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
  * or implied. See the License for the specific language governing permissions and limitations under
@@ -210,6 +210,9 @@ public class CodeGenMojo extends AbstractMojo {
 
     /**
      * A map of additional properties that can be referenced by the mustache templates
+     * <additionalProperties>
+     *     <additionalProperty>key=value</additionalProperty>
+     * </additionalProperties>
      */
     @Parameter(name = "additionalProperties")
     private List<String> additionalProperties;
@@ -218,7 +221,7 @@ public class CodeGenMojo extends AbstractMojo {
      * A map of reserved names and how they should be escaped
      */
     @Parameter(name = "reservedWordsMappings")
-    private List<String> reservedWordsMappings;    
+    private List<String> reservedWordsMappings;
 
     /**
      * Generate the apis
@@ -466,32 +469,32 @@ public void execute() throws MojoExecutionException {
         }
 
         //Apply Instantiation Types
-        if (instantiationTypes != null && !configOptions.containsKey("instantiation-types")) {
+        if (instantiationTypes != null && (configOptions == null || !configOptions.containsKey("instantiation-types"))) {
             applyInstantiationTypesKvpList(instantiationTypes, configurator);
         }
 
         //Apply Import Mappings
-        if (importMappings != null && !configOptions.containsKey("import-mappings")) {
+        if (importMappings != null && (configOptions == null || !configOptions.containsKey("import-mappings"))) {
             applyImportMappingsKvpList(importMappings, configurator);
         }
 
         //Apply Type Mappings
-        if (typeMappings != null && !configOptions.containsKey("type-mappings")) {
+        if (typeMappings != null && (configOptions == null || !configOptions.containsKey("type-mappings"))) {
             applyTypeMappingsKvpList(typeMappings, configurator);
         }
 
         //Apply Language Specific Primitives
-        if (languageSpecificPrimitives != null && !configOptions.containsKey("language-specific-primitives")) {
+        if (languageSpecificPrimitives != null && (configOptions == null || !configOptions.containsKey("language-specific-primitives"))) {
             applyLanguageSpecificPrimitivesCsvList(languageSpecificPrimitives, configurator);
         }
 
         //Apply Additional Properties
-        if (additionalProperties != null && !configOptions.containsKey("additional-properties")) {
+        if (additionalProperties != null && (configOptions == null || !configOptions.containsKey("additional-properties"))) {
             applyAdditionalPropertiesKvpList(additionalProperties, configurator);
         }
 
         //Apply Reserved Words Mappings
-        if (reservedWordsMappings != null && !configOptions.containsKey("reserved-words-mappings")) {
+        if (reservedWordsMappings != null && (configOptions == null || !configOptions.containsKey("reserved-words-mappings"))) {
             applyReservedWordsMappingsKvpList(reservedWordsMappings, configurator);
         }