diff --git a/mozilla/tools/footprint/wm.cpp b/mozilla/tools/footprint/wm.cpp
index 4215e3e3587..af9cbe10167 100644
--- a/mozilla/tools/footprint/wm.cpp
+++ b/mozilla/tools/footprint/wm.cpp
@@ -583,12 +583,16 @@ main(int argc, char* argv[])
         }
     }
 
-    {
+    if (argv[i]) {
         char* p = argv[i];
         wchar_t* q = process_name;
         while (*q++ = wchar_t(*p++))
             continue;
     }
+    else {
+        fprintf(stderr, "no image name specified\n");
+        exit(1);
+    }
 
     init_entries();