diff --git a/RMMapper/NSUserDefaults+RMSaveCustomObject.m b/RMMapper/NSUserDefaults+RMSaveCustomObject.m
index b2fdc30..3bd17ee 100644
--- a/RMMapper/NSUserDefaults+RMSaveCustomObject.m
+++ b/RMMapper/NSUserDefaults+RMSaveCustomObject.m
@@ -23,9 +23,14 @@ -(void)rm_setCustomObject:(id)obj forKey:(NSString *)key {
 
 -(id)rm_customObjectForKey:(NSString *)key {
     NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
-    NSData *encodedObject = [defaults objectForKey:key];
-    id obj = [NSKeyedUnarchiver unarchiveObjectWithData:encodedObject];
-    return obj;
+    if ([[defaults dictionaryRepresentation].allKeys containsObject:key]) {
+        NSData *encodedObject = [defaults objectForKey:key];
+        id obj = [NSKeyedUnarchiver unarchiveObjectWithData:encodedObject];
+        return obj;
+        // unarchive the value here
+    }else{
+        return nil;
+    }
 }
 
 @end
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