diff --git a/codegen/smithy-dafny-codegen/src/main/java/software/amazon/polymorph/smithydotnet/TypeConversionCodegen.java b/codegen/smithy-dafny-codegen/src/main/java/software/amazon/polymorph/smithydotnet/TypeConversionCodegen.java
index 8b4455fc7..aa19e7bfe 100644
--- a/codegen/smithy-dafny-codegen/src/main/java/software/amazon/polymorph/smithydotnet/TypeConversionCodegen.java
+++ b/codegen/smithy-dafny-codegen/src/main/java/software/amazon/polymorph/smithydotnet/TypeConversionCodegen.java
@@ -558,7 +558,6 @@ public TypeConverter generateUnionConverter(final UnionShape unionShape) {
             .of(defNames
                 .stream()
                 .map(memberShape -> {
-                    final String propertyNameEdgeCase = StringUtils.equals(nameResolver.classPropertyForStructureMember(memberShape), "KmsKeyArn") ? "kmsKeyArn" : nameResolver.classPropertyForStructureMember(memberShape);
                     final String propertyName = nameResolver.classPropertyForStructureMember(memberShape);
                     final String memberFromDafnyConverterName = typeConverterForShape(
                             memberShape.getId(), FROM_DAFNY);
@@ -569,7 +568,7 @@ public TypeConverter generateUnionConverter(final UnionShape unionShape) {
                         destructorValue = DafnyNameResolverHelpers.dafnyCompilesExtra_(memberShape.getMemberName());
                     }
                     return TokenTree
-                            .of("if (value.is_%s)".formatted(propertyNameEdgeCase))
+                            .of("if (value.is_%s)".formatted(memberShape.getMemberName()))
                             .append(TokenTree
                                     .of(
                                             "converted.%s = %s(concrete.dtor_%s);"