diff --git a/programs/dxdiag/main.c b/programs/dxdiag/main.c
index 54bb84f827c..3ced122d6e7 100644
--- a/programs/dxdiag/main.c
+++ b/programs/dxdiag/main.c
@@ -80,7 +80,7 @@ static BOOL process_file_name(const WCHAR *cmdline, enum output_type output_type
     filename[len] = '\0';
 
     /* Append an extension appropriate for the output type if the filename does not have one. */
-    if (!(endptr = strrchrW(filename, '.')))
+    if (!strrchrW(filename, '.'))
     {
         const WCHAR *filename_ext = get_output_extension(output_type);