diff --git a/mapKey.js b/mapKey.js
index 8ad4b8c20..d2488c9ae 100644
--- a/mapKey.js
+++ b/mapKey.js
@@ -1,5 +1,3 @@
-import baseAssignValue from './.internal/baseAssignValue.js'
-
 /**
  * The opposite of `mapValue` this method creates an object with the
  * same values as `object` and keys generated by running each own enumerable
@@ -21,8 +19,9 @@ import baseAssignValue from './.internal/baseAssignValue.js'
  */
 function mapKey(object, iteratee) {
   const result = {}
-  Object.keys(object).forEach((value, key, object) => {
-    baseAssignValue(result, iteratee(value, key, object), value)
+  Object.keys(Object(object)).forEach((key) => {
+    const value = object[key]
+    result[iteratee(value, key, object)] = value
   })
   return result
 }
diff --git a/mapValue.js b/mapValue.js
index 9a49776f5..31e0c1dde 100644
--- a/mapValue.js
+++ b/mapValue.js
@@ -1,5 +1,3 @@
-import baseAssignValue from './.internal/baseAssignValue.js'
-
 /**
  * Creates an object with the same keys as `object` and values generated
  * by running each own enumerable string keyed property of `object` thru
@@ -24,8 +22,8 @@ import baseAssignValue from './.internal/baseAssignValue.js'
  */
 function mapValue(object, iteratee) {
   const result = {}
-  Object.keys(object).forEach((value, key, object) => {
-    baseAssignValue(result, key, iteratee(value, key, object))
+  Object.keys(Object(object)).forEach((key) => {
+    result[key] = iteratee(object[value], key, object)
   })
   return result
 }