diff --git a/lodash.src.js b/lodash.src.js
index be65b2cd9..d94f1772c 100644
--- a/lodash.src.js
+++ b/lodash.src.js
@@ -331,6 +331,20 @@
     return -1;
   }
 
+  /**
+   * The base implementation of `_.isFunction` without support for environments
+   * with incorrect `typeof` results.
+   *
+   * @private
+   * @param {*} value The value to check.
+   * @returns {boolean} Returns `true` if `value` is correctly classified, else `false`.
+   */
+  function baseIsFunction(value) {
+    // Avoid a Chakra JIT bug in compatibility modes of IE 11.
+    // See https://github.com/jashkenas/underscore/issues/1621 for more details.
+    return typeof value == 'function' || false;
+  }
+
   /**
    * The base implementation of `_.sortBy` and `_.sortByAll` which uses `comparer`
    * to define the sort order of `array` and replaces criteria objects with their
@@ -7502,7 +7516,7 @@
       if (!length) {
         return function() { return arguments[0]; };
       }
-      if (!arrayEvery(funcs, isFunction)) {
+      if (!arrayEvery(funcs, baseIsFunction)) {
         throw new TypeError(FUNC_ERROR_TEXT);
       }
       return function() {
@@ -7547,7 +7561,7 @@
       if (fromIndex < 0) {
         return function() { return arguments[0]; };
       }
-      if (!arrayEvery(funcs, isFunction)) {
+      if (!arrayEvery(funcs, baseIsFunction)) {
         throw new TypeError(FUNC_ERROR_TEXT);
       }
       return function() {
@@ -8297,20 +8311,12 @@
      * _.isFunction(/abc/);
      * // => false
      */
-    function isFunction(value) {
-      // Avoid a Chakra JIT bug in compatibility modes of IE 11.
-      // See https://github.com/jashkenas/underscore/issues/1621 for more details.
-      return typeof value == 'function' || false;
-    }
-    // Fallback for environments that return incorrect `typeof` operator results.
-    if (isFunction(/x/) || (Uint8Array && !isFunction(Uint8Array))) {
-      isFunction = function(value) {
-        // The use of `Object#toString` avoids issues with the `typeof` operator
-        // in older versions of Chrome and Safari which return 'function' for regexes
-        // and Safari 8 equivalents which return 'object' for typed array constructors.
-        return objToString.call(value) == funcTag;
-      };
-    }
+    var isFunction = !(baseIsFunction(/x/) || (Uint8Array && !baseIsFunction(Uint8Array))) ? baseIsFunction : function(value) {
+      // The use of `Object#toString` avoids issues with the `typeof` operator
+      // in older versions of Chrome and Safari which return 'function' for regexes
+      // and Safari 8 equivalents which return 'object' for typed array constructors.
+      return objToString.call(value) == funcTag;
+    };
 
     /**
      * Checks if `value` is the language type of `Object`.