--- a/Makefile.in
+++ b/Makefile.in
@@ -170,17 +170,17 @@ NO_REMOVE=1
 endif
 
 # For an artifact build, _tests will already be partly populated, so run
 # this install manifest with NO_REMOVE set in this case.
 ifdef MOZ_ARTIFACT_BUILDS
 install-_tests: NO_REMOVE=1
 endif
 
-.PHONY: $(addprefix install-,$(subst /,_,$(install_manifests)))
+.PHONY: $(addprefix install-,$(install_manifests))
 $(addprefix install-,$(install_manifests)): install-%: $(install_manifest_depends)
 ifneq (,$(filter FasterMake+RecursiveMake,$(BUILD_BACKENDS)))
 	@# If we're using the hybrid FasterMake/RecursiveMake backend, we want
 	@# to ensure the FasterMake end doesn't have install manifests for the
 	@# same directory, because that would blow up
 	$(if $(wildcard _build_manifests/install/$(subst /,_,$*)),$(if $(wildcard faster/install_$(subst /,_,$*)*),$(error FasterMake and RecursiveMake ends of the hybrid build system want to handle $*)))
 endif
 	$(addprefix $(call py_action,process_install_manifest,$(if $(NO_REMOVE),--no-remove )$*) ,$(wildcard _build_manifests/install/$(subst /,_,$*)))