diff --git a/modules/plugin/Makefile.in b/modules/plugin/Makefile.in
index aef5287e3c4d..d1013d73f783 100644
--- a/modules/plugin/Makefile.in
+++ b/modules/plugin/Makefile.in
@@ -68,9 +68,11 @@ ifeq ($(OS_ARCH),OS2)
 TOOL_DIRS += default/os2
 endif
 
+ifdef PBBUILD
 ifeq ($(MOZ_WIDGET_TOOLKIT),cocoa)
 TOOL_DIRS += default/mac
 endif
+endif
 
 ifdef ENABLE_TESTS
 ifneq (,$(filter WINNT Darwin Linux OS2 SunOS,$(OS_ARCH)))