diff --git a/master/custom/factories.py b/master/custom/factories.py
index 21a6a705..49d7b9ea 100644
--- a/master/custom/factories.py
+++ b/master/custom/factories.py
@@ -1276,7 +1276,7 @@ def setup(self, parallel, branch, **kwargs):
             "--gen-suppressions=all",
             "--track-origins=yes",
             "--trace-children=yes",
-            "--suppressions=./Misc/valgrind-python.supp",
+            util.Interpolate("--suppressions=%(prop:builddir)s/build/Misc/valgrind-python.supp"),
             "./python",
             "-m", "test",
             *self.testFlags,