diff --git a/Makefile.am b/Makefile.am
index dfd83700f305cdae0bf0f1e1d78846afa522c7e3..24f6f22ec5a7db4a0dda9999eaf3b854ecc1f639 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1631,6 +1631,7 @@ endif
 
 .PHONY: py-apidoc
 py-apidoc: epydoc.conf $(RUN_IN_TEMPDIR) $(GENERATED_FILES)
+	env - PATH="$$PATH" PYTHONPATH="$$PYTHONPATH" \
 	$(RUN_IN_TEMPDIR) epydoc -v \
 	  --conf $(CURDIR)/epydoc.conf \
 	  --output $(CURDIR)/$(APIDOC_PY_DIR)