diff --git a/packages/typescript/src/interface-factory.ts b/packages/typescript/src/interface-factory.ts
index f7ceea3..62238fa 100644
--- a/packages/typescript/src/interface-factory.ts
+++ b/packages/typescript/src/interface-factory.ts
@@ -289,7 +289,7 @@ function* buildType(type: Type): Iterable<string> {
 
         const recordType = `Record<${keyTypeName}, ${Array.from(typeNames)
           .sort()
-          .join(' | ')}>`;
+          .join(' | ')} ${mapValue.value.isNullable ? ` | null` : ''}>`;
 
         yield isEnumKey ? `Partial<${recordType}>` : recordType;
       }
diff --git a/packages/typescript/src/spec/4.1-structure/4.1.12-primitive-value.spec.ts b/packages/typescript/src/spec/4.1-structure/4.1.12-primitive-value.spec.ts
index 02ccf95..710317d 100644
--- a/packages/typescript/src/spec/4.1-structure/4.1.12-primitive-value.spec.ts
+++ b/packages/typescript/src/spec/4.1-structure/4.1.12-primitive-value.spec.ts
@@ -241,9 +241,7 @@ describe('4.1.12 Primitive Value', () => {
       );
     });
 
-    // TODO: fix and enable these tests
-    // https://github.com/basketry/typescript/issues/139
-    describe.skip('map property value', () => {
+    describe('map property value', () => {
       it.each(typeMap)(
         'emits nullable `%s` as a union of `%s` and null',
         async (primitive, expectedType) => {
@@ -407,9 +405,7 @@ describe('4.1.12 Primitive Value', () => {
       );
     });
 
-    // TODO: fix and enable these tests
-    // https://github.com/basketry/typescript/issues/139
-    describe.skip('map property value', () => {
+    describe('map property value', () => {
       it.each(typeMap)(
         'emits `%s` as a union of `%s` array and null',
         async (primitive, expectedType) => {
@@ -577,9 +573,7 @@ describe('4.1.12 Primitive Value', () => {
       );
     });
 
-    // TODO: fix and enable these tests
-    // https://github.com/basketry/typescript/issues/139
-    describe.skip('map property value', () => {
+    describe('map property value', () => {
       it.each(typeMap)(
         'emits nullable `%s` as a union of `%s` and null',
         async (primitive, expectedType) => {
@@ -665,9 +659,7 @@ describe('4.1.12 Primitive Value', () => {
       );
     });
 
-    // TODO: fix and enable these tests
-    // https://github.com/basketry/typescript/issues/139
-    describe.skip('map property value', () => {
+    describe('map property value', () => {
       it.each(typeMap)(
         'emits `%s` as a union of `%s` array and null',
         async (primitive, expectedType) => {