diff --git a/mozilla/xpcom/reflect/xptcall/src/md/unix/Makefile.in b/mozilla/xpcom/reflect/xptcall/src/md/unix/Makefile.in
index cea265ec81d..9853613e2fe 100644
--- a/mozilla/xpcom/reflect/xptcall/src/md/unix/Makefile.in
+++ b/mozilla/xpcom/reflect/xptcall/src/md/unix/Makefile.in
@@ -51,7 +51,7 @@ REQUIRES = string
 #
 # The default is this buildable, but non-functioning code.
 #
-CPPSRCS		:= xptcinvoke_unsupported.cpp xptcstubs_unsupported.cpp
+CPPSRCS = $(error XPTCall not implemented on this platform!)
 
 # Force use of PIC
 FORCE_USE_PIC	= 1