--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -25,7 +25,7 @@ def explain_exit(code):
         val = os.WTERMSIG(code)
         return "killed by signal %d" % val, val
     elif os.WIFSTOPPED(code):
-        val = os.STOPSIG(code)
+        val = os.WSTOPSIG(code)
         return "stopped by signal %d" % val, val
     raise ValueError("invalid exit code")