diff --git a/tools/pyflakes.sh b/tools/pyflakes.sh
index c28b1012..5f5a053b 100755
--- a/tools/pyflakes.sh
+++ b/tools/pyflakes.sh
@@ -2,4 +2,7 @@
 if [ `basename $PWD` == 'tools' ]; then
         cd ..
 fi
-pyflakes weboob scripts/* | grep -v __init__.py
+
+# grep will return 0 only if it founds something, but our script
+# wants to return 0 when it founds nothing!
+pyflakes weboob scripts/* | grep -v redefinition && exit 1 || exit 0