diff --git a/SSZipArchive.m b/SSZipArchive.m
index 410264f..b3936eb 100644
--- a/SSZipArchive.m
+++ b/SSZipArchive.m
@@ -305,7 +305,7 @@
         NSDirectoryEnumerator *dirEnumerator = [fileManager enumeratorAtPath:directoryPath];
         
 		NSString *fileName;
-        while (fileName = [dirEnumerator nextObject]) {
+        while ((fileName = [dirEnumerator nextObject])) {
             BOOL isDir;
             NSString *fullFilePath = [directoryPath stringByAppendingPathComponent:fileName];
             [fileManager fileExistsAtPath:fullFilePath isDirectory:&isDir];