diff --git a/YTKNetwork/YTKNetworkAgent.m b/YTKNetwork/YTKNetworkAgent.m
index 5703013..a0ae14c 100644
--- a/YTKNetwork/YTKNetworkAgent.m
+++ b/YTKNetwork/YTKNetworkAgent.m
@@ -549,7 +549,10 @@ - (NSURL *)incompleteDownloadTempPathForDownloadPath:(NSString *)downloadPath {
     NSString *tempPath = nil;
     NSString *md5URLString = [YTKNetworkUtils md5StringFromString:downloadPath];
     tempPath = [[self incompleteDownloadTempCacheFolder] stringByAppendingPathComponent:md5URLString];
-    return [NSURL fileURLWithPath:tempPath];
+    if (tempPath) {
+        return [NSURL fileURLWithPath:tempPath];
+    }
+    return nil;
 }
 
 #pragma mark - Testing
diff --git a/YTKNetwork/YTKNetworkPrivate.m b/YTKNetwork/YTKNetworkPrivate.m
index 1bc62e1..200f2d2 100644
--- a/YTKNetwork/YTKNetworkPrivate.m
+++ b/YTKNetwork/YTKNetworkPrivate.m
@@ -92,6 +92,9 @@ + (BOOL)validateJSON:(id)json withValidator:(id)jsonValidator {
 }
 
 + (void)addDoNotBackupAttribute:(NSString *)path {
+    if (!path) {
+        return ;
+    }
     NSURL *url = [NSURL fileURLWithPath:path];
     NSError *error = nil;
     [url setResourceValue:[NSNumber numberWithBool:YES] forKey:NSURLIsExcludedFromBackupKey error:&error];