diff --git a/mozilla/client.mk b/mozilla/client.mk
index 5c4ef7b02e2..8d4662ebca1 100644
--- a/mozilla/client.mk
+++ b/mozilla/client.mk
@@ -418,6 +418,9 @@ CVS = cvs
 comma := ,
 
 CWD := $(shell pwd)
+ifneq (1,$(words $(CWD)))
+$(error The mozilla directory cannot be located in a path with spaces.)
+endif
 
 ifeq "$(CWD)" "/"
 CWD   := /.