diff --git a/SDWebImage.xcodeproj/project.pbxproj b/SDWebImage.xcodeproj/project.pbxproj
index 1747cd6..e30fc04 100644
--- a/SDWebImage.xcodeproj/project.pbxproj
+++ b/SDWebImage.xcodeproj/project.pbxproj
@@ -1350,6 +1350,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
+				CLANG_ANALYZER_NONNULL = YES;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
@@ -1410,6 +1411,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
+				CLANG_ANALYZER_NONNULL = YES;
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
diff --git a/SDWebImage/SDWebImageManager.m b/SDWebImage/SDWebImageManager.m
index 6318e00..b213cec 100644
--- a/SDWebImage/SDWebImageManager.m
+++ b/SDWebImage/SDWebImageManager.m
@@ -140,8 +140,10 @@
     __weak SDWebImageCombinedOperation *weakOperation = operation;
 
     BOOL isFailedUrl = NO;
-    @synchronized (self.failedURLs) {
-        isFailedUrl = [self.failedURLs containsObject:url];
+    if (url) {
+        @synchronized (self.failedURLs) {
+            isFailedUrl = [self.failedURLs containsObject:url];
+        }
     }
 
     if (url.absoluteString.length == 0 || (!(options & SDWebImageRetryFailed) && isFailedUrl)) {