diff --git a/src/Makefile.global.in b/src/Makefile.global.in
index 5dacc4d838..7d5e08c667 100644
--- a/src/Makefile.global.in
+++ b/src/Makefile.global.in
@@ -464,7 +464,7 @@ rm -rf '$(CURDIR)'/tmp_check && \
 $(MKDIR_P) '$(CURDIR)'/tmp_check && \
 cd $(srcdir) && \
    TESTDIR='$(CURDIR)' PATH="$(bindir):$(CURDIR):$$PATH" \
-   PGPORT='6$(DEF_PGPORT)' top_builddir='$(top_builddir)' \
+   PGPORT='6$(DEF_PGPORT)' \
    PG_REGRESS='$(top_builddir)/src/test/regress/pg_regress' \
    $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) $(if $(PROVE_TESTS),$(PROVE_TESTS),t/*.pl)
 endef