diff --git a/js/src/build/Makefile.in b/js/src/build/Makefile.in
index 09063a19602f..0d5e980e8254 100644
--- a/js/src/build/Makefile.in
+++ b/js/src/build/Makefile.in
@@ -30,8 +30,9 @@ install:: $(LIBRARY_NAME).pc
 	cp $^ $(JS_LIBRARY_NAME).pc
 	$(SYSINSTALL) $(JS_LIBRARY_NAME).pc $(DESTDIR)$(libdir)/pkgconfig
 
-install:: ../js-config.h
-	$(SYSINSTALL) $^ $(DESTDIR)$(includedir)/$(JS_LIBRARY_NAME)
+install:: ../js-config.h ../js-confdefs.h
+	$(SYSINSTALL) -m644 ../js-config.h $(DESTDIR)$(includedir)/$(JS_LIBRARY_NAME)
+	$(SYSINSTALL) -m644 ../js-confdefs.h $(DESTDIR)$(includedir)/$(JS_LIBRARY_NAME)
 
 ######################################################
 # BEGIN SpiderMonkey header installation
diff --git a/js/src/build/js-config.in b/js/src/build/js-config.in
index 9cd41d613de5..2faa3001f409 100644
--- a/js/src/build/js-config.in
+++ b/js/src/build/js-config.in
@@ -108,7 +108,7 @@ if test "$echo_libdir" = "yes"; then
 fi
 
 if test "$echo_cflags" = "yes"; then
-    echo "-std=gnu++11 -include $includedir/$JS_LIBRARY_NAME/js/RequiredDefines.h -I$includedir/$JS_LIBRARY_NAME $NSPR_CFLAGS"
+    echo "-std=gnu++11 -include $includedir/$JS_LIBRARY_NAME/js-confdefs.h -isystem $includedir/$JS_LIBRARY_NAME $NSPR_CFLAGS"
 fi
 
 if test "$echo_libs" = "yes"; then
diff --git a/js/src/build/js.pc.in b/js/src/build/js.pc.in
index d40deb174f6c..a65acb62feb0 100644
--- a/js/src/build/js.pc.in
+++ b/js/src/build/js.pc.in
@@ -11,4 +11,4 @@ Libs: -L${libdir} -l@JS_LIBRARY_NAME@
 # Use -isystem for includes rather than -I, to mark them as "system headers"
 # that don't generate warning diagnostics. For justification, see
 # https://bugzilla.mozilla.org/show_bug.cgi?id=1539036
-Cflags: -include ${includedir}/@JS_LIBRARY_NAME@/js/RequiredDefines.h -isystem ${includedir}/@JS_LIBRARY_NAME@
+Cflags: -include ${includedir}/@JS_LIBRARY_NAME@/js-confdefs.h -isystem ${includedir}/@JS_LIBRARY_NAME@