diff --git a/mozilla/layout/build/Makefile.in b/mozilla/layout/build/Makefile.in
index 02210a0fa52..d50e283a8bb 100644
--- a/mozilla/layout/build/Makefile.in
+++ b/mozilla/layout/build/Makefile.in
@@ -241,6 +241,11 @@ EXTRA_DSO_LDOPTS += \
 	$(NULL)
 endif
 
+# Add explicit X11 dependency when building against X11 toolkits
+ifneq (,$(filter gtk gtk2 qt xlib,$(MOZ_WIDGET_TOOLKIT)))
+EXTRA_DSO_LDOPTS += $(XLDFLAGS) $(XLIBS)
+endif
+
 include $(topsrcdir)/config/rules.mk
 
 LOCAL_INCLUDES	+= -I$(srcdir)/../base \