diff --git a/browser/installer/moz.build b/browser/installer/moz.build
deleted file mode 100644
index 895d11993cfb..000000000000
--- a/browser/installer/moz.build
+++ /dev/null
@@ -1,6 +0,0 @@
-# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
-# vim: set filetype=python:
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
diff --git a/config/makefiles/target_libs.mk b/config/makefiles/target_libs.mk
index fc4e3d2a14a9..e6083463117b 100644
--- a/config/makefiles/target_libs.mk
+++ b/config/makefiles/target_libs.mk
@@ -108,12 +108,12 @@ BINARIES_INSTALL_TARGETS := $(foreach category,$(INSTALL_TARGETS),$(if $(filter
 # and with dependencies on the relevant backend files.
 BINARIES_PP := $(MDDEPDIR)/binaries.pp
 
-$(BINARIES_PP): Makefile $(if $(EXTERNALLY_MANAGED_MAKE_FILE),,backend.mk) $(call mkdir_deps,$(MDDEPDIR))
+$(BINARIES_PP): Makefile $(wildcard backend.mk) $(call mkdir_deps,$(MDDEPDIR))
 	@echo "$(strip $(foreach category,$(BINARIES_INSTALL_TARGETS),\
 		$(foreach file,$($(category)_FILES) $($(category)_EXECUTABLES),\
 			$($(category)_DEST)/$(notdir $(file)): $(file)%\
 		)\
-	))binaries: Makefile $(if $(EXTERNALLY_MANAGED_MAKE_FILE),,backend.mk)" | tr % '\n' > $@
+	))binaries: Makefile $(wildcard backend.mk)" | tr % '\n' > $@
 
 else
 binaries::
diff --git a/js/src/config/makefiles/target_libs.mk b/js/src/config/makefiles/target_libs.mk
index fc4e3d2a14a9..e6083463117b 100644
--- a/js/src/config/makefiles/target_libs.mk
+++ b/js/src/config/makefiles/target_libs.mk
@@ -108,12 +108,12 @@ BINARIES_INSTALL_TARGETS := $(foreach category,$(INSTALL_TARGETS),$(if $(filter
 # and with dependencies on the relevant backend files.
 BINARIES_PP := $(MDDEPDIR)/binaries.pp
 
-$(BINARIES_PP): Makefile $(if $(EXTERNALLY_MANAGED_MAKE_FILE),,backend.mk) $(call mkdir_deps,$(MDDEPDIR))
+$(BINARIES_PP): Makefile $(wildcard backend.mk) $(call mkdir_deps,$(MDDEPDIR))
 	@echo "$(strip $(foreach category,$(BINARIES_INSTALL_TARGETS),\
 		$(foreach file,$($(category)_FILES) $($(category)_EXECUTABLES),\
 			$($(category)_DEST)/$(notdir $(file)): $(file)%\
 		)\
-	))binaries: Makefile $(if $(EXTERNALLY_MANAGED_MAKE_FILE),,backend.mk)" | tr % '\n' > $@
+	))binaries: Makefile $(wildcard backend.mk)" | tr % '\n' > $@
 
 else
 binaries::