diff --git a/types/lodash/index.d.ts b/types/lodash/index.d.ts
index b0e4f6848d..7162d4b2da 100644
--- a/types/lodash/index.d.ts
+++ b/types/lodash/index.d.ts
@@ -9515,7 +9515,7 @@ declare namespace _ {
          * @param value The value to check.
          * @return Returns true if value is correctly classified, else false.
          */
-        isFunction(value?: any): value is (...args: any[]) => any;
+        isFunction(value: any): value is (...args: any[]) => any;
     }
 
     interface LoDashImplicitWrapper<TValue> {
diff --git a/types/lodash/lodash-tests.ts b/types/lodash/lodash-tests.ts
index c7fb313dec..1977626262 100644
--- a/types/lodash/lodash-tests.ts
+++ b/types/lodash/lodash-tests.ts
@@ -8060,7 +8060,11 @@ namespace TestIsFunction {
             let result: Function = value;
         }
         else {
-            let result: number = value;
+            let result: number|Function = value;
+        }
+
+        if (_.isFunction(any)) {
+            any();
         }
     }