diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
index d32fc8d..10b515b 100755
--- a/Lib/test/regrtest.py
+++ b/Lib/test/regrtest.py
@@ -412,6 +412,8 @@
         usage("-T and -j don't go together!")
     if use_mp and findleaks:
         usage("-l and -j don't go together!")
+    if use_mp and support.max_memuse:
+        usage("-M and -j don't go together!")
     if failfast and not (verbose or verbose3):
         usage("-G/--failfast needs either -v or -W")