diff --git a/js/src/xpconnect/src/Makefile.in b/js/src/xpconnect/src/Makefile.in
index fc42bca7a0f..27552738306 100644
--- a/js/src/xpconnect/src/Makefile.in
+++ b/js/src/xpconnect/src/Makefile.in
@@ -151,7 +151,7 @@ endif
 # the windows ce compiler produces crap when compiling this
 # with any optimizations.  See bug 304714
 ifdef WINCE
-MOZ_OPTIMIZE_FLAGS=/Od
+MOZ_OPTIMIZE_FLAGS=-Od
 endif
 
 ifeq ($(OS_ARCH),WINNT)