diff --git a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/cpp/PlatformAndKeywordSanitizer.java b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/cpp/PlatformAndKeywordSanitizer.java
index 0035c50d12b..a4df6df5b8d 100644
--- a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/cpp/PlatformAndKeywordSanitizer.java
+++ b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/domainmodels/codegeneration/cpp/PlatformAndKeywordSanitizer.java
@@ -166,6 +166,17 @@ public class PlatformAndKeywordSanitizer {
     public static String fixEnumValue (String enumValue) {
         String enumMemberName = enumValue;
 
+        // NOT_SET is a special value in C++ SDK enums used in two scenarios:
+        // 1. When an enum cannot be deserialized from a string value
+        // 2. When accessing an enum created from an invalid string value
+        // Note: Services may still use NOT_SET as a valid key in maps
+        //
+        // TODO: model this as a crt or std optional to represent "absent of value"
+        //       instead of using a common-ish predetermined value.
+        if (enumValue.equals("NOT_SET")) {
+            return "NOT_SET_VALUE";
+        }
+
         for (String invalid : ENUM_CHARS_MAPPING.keySet()) {
             enumMemberName = enumMemberName.replace(invalid, ENUM_CHARS_MAPPING.get(invalid));
         }