diff --git a/lib/replace-in-file.js b/lib/replace-in-file.js
index 6fd19e1..cf9d0c5 100644
--- a/lib/replace-in-file.js
+++ b/lib/replace-in-file.js
@@ -20,7 +20,7 @@ function replaceInFile(config, cb) {
     config = parseConfig(config);
   }
   catch (error) {
-    if (cb) {
+    if (typeof cb === "function") {
       return cb(error, null);
     }
     return Promise.reject(error);
@@ -45,7 +45,7 @@ function replaceInFile(config, cb) {
 
     //Success handler
     .then(results => {
-      if (cb) {
+      if (typeof cb === "function") {
         cb(null, results);
       }
       return results;
@@ -53,7 +53,7 @@ function replaceInFile(config, cb) {
 
     //Error handler
     .catch(error => {
-      if (cb) {
+      if (typeof cb === "function") {
         cb(error);
       }
       else {