diff --git a/tests/hghave b/tests/hghave
index d566aa319d5f7c58c69b985b53ff7498f08e53c6_dGVzdHMvaGdoYXZl..40d930848fd01522618be181277dd6ad5ef7f08a_dGVzdHMvaGdoYXZl 100755
--- a/tests/hghave
+++ b/tests/hghave
@@ -202,7 +202,7 @@
         os.rmdir(d)
 
 def has_pyflakes():
-    return matchoutput('echo "import re" 2>&1 | pyflakes',
+    return matchoutput("sh -c \"echo 'import re' 2>&1 | pyflakes\"",
                        r"<stdin>:1: 're' imported but unused",
                        True)