diff --git a/src/serializers/postman/v2.0/Serializer.js b/src/serializers/postman/v2.0/Serializer.js
index 1920695..812e59b 100644
--- a/src/serializers/postman/v2.0/Serializer.js
+++ b/src/serializers/postman/v2.0/Serializer.js
@@ -620,7 +620,7 @@ methods.createHeaderFromParameter = (param) => {
     return { key, value: schema.enum[0] }
   }
 
-  return { key, value: null }
+  return { key, value: '' }
 }
 
 /**
diff --git a/src/serializers/postman/v2.0/__tests__/Serializer.spec.js b/src/serializers/postman/v2.0/__tests__/Serializer.spec.js
index 94ffeb4..711d41e 100644
--- a/src/serializers/postman/v2.0/__tests__/Serializer.spec.js
+++ b/src/serializers/postman/v2.0/__tests__/Serializer.spec.js
@@ -844,7 +844,7 @@ describe('serializers/swagger/v2.0/Serializer.js', () => {
       ]
       const expected = [
         null,
-        { key: 123, value: null },
+        { key: 123, value: '' },
         { key: 234, value: 'abc' },
         { key: 345, value: 'def' }
       ]
diff --git a/testing/e2e/internal-postman2/test-case-0/output.json b/testing/e2e/internal-postman2/test-case-0/output.json
index 91c1177..8759556 100644
--- a/testing/e2e/internal-postman2/test-case-0/output.json
+++ b/testing/e2e/internal-postman2/test-case-0/output.json
@@ -170,7 +170,7 @@
             "header": [
               {
                 "key": "api_key",
-                "value": null
+                "value": ""
               },
               {
                 "key": "Content-Type",
@@ -362,4 +362,4 @@
       "name": "Content-Type"
     }
   ]
-}
\ No newline at end of file
+}