diff --git a/tests/Makefile.am b/tests/Makefile.am
index e56e528e..d3153a55 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -14,6 +14,7 @@ TESTS_ENVIRONMENT = \
   NIX_BUILD_HOOK=					\
   PGHOST=/tmp	\
   PERL5LIB="$(srcdir):$(abs_top_srcdir)/src/lib:$$PERL5LIB"	\
+  PYTHONPATH= \
   PATH=$(abs_top_srcdir)/src/hydra-evaluator:$(abs_top_srcdir)/src/script:$(abs_top_srcdir)/src/hydra-eval-jobs:$(abs_top_srcdir)/src/hydra-queue-runner:$$PATH \
   perl -w