diff --git a/Makefile.defs b/Makefile.defs
index 5cce62f1d..5f4c65c68 100644
--- a/Makefile.defs
+++ b/Makefile.defs
@@ -60,7 +60,7 @@ endif
 
 ifeq ($(USE_BREW),1)
   BREW_PREFIX = $(shell brew --prefix 2>/dev/null)
-  ifeq ($(BREW_PREFIX),)
+  ifeq ($(strip $(BREW_PREFIX)),)
     MACPORTS_PREFIX = /opt/local
   endif
 endif