--- a/Makefile.in
+++ b/Makefile.in
@@ -101,17 +101,17 @@ install-manifests: $(addprefix install-d
 
 .PHONY: $(addprefix install-dist-,$(install_manifests))
 $(addprefix install-dist-,$(install_manifests)): install-dist-%: $(install_manifest_depends)
 	$(call py_action,process_install_manifest,$(if $(NO_REMOVE),--no-remove )$(DIST)/$* _build_manifests/install/dist_$* $(if $(LIBXUL_SDK),,js/src/_build_manifests/install/dist_$*))
 
 .PHONY: install-tests
 install-manifests: install-tests
 install-tests: $(install_manifest_depends)
-	$(call py_action,process_install_manifest,$(if $(NO_REMOVE),--no-remove )_tests _build_manifests/install/tests js/src/_build_manifests/install/tests)
+	$(call py_action,process_install_manifest,$(if $(NO_REMOVE),--no-remove )_tests _build_manifests/install/tests $(if $(LIBXUL_SDK),,js/src/_build_manifests/install/tests))
 
 
 # _tests should be purged during cleaning. However, we don't want it purged
 # during PGO builds because it contains some auto-generated files.
 ifneq ($(filter-out maybe_clobber_profiledbuild,$(MAKECMDGOALS)),)
 GARBAGE_DIRS += _tests
 endif