diff --git a/gmp/config.mk.in b/gmp/config.mk.in
index 08cd1979148930ac480fc578d79384e8b18b2a9e..1937bc4f866deb587421080e6baf85e4983e67b3 100644
--- a/gmp/config.mk.in
+++ b/gmp/config.mk.in
@@ -1,8 +1,7 @@
-
-ifeq ($(HaveLibGmp),"")
+ifeq "$(HaveLibGmp)" ""
  HaveLibGmp = @HaveLibGmp@
 endif
 
-ifeq ($(HaveFrameworkGMP),"")
+ifeq "$(HaveFrameworkGMP)" ""
  HaveFrameworkGMP = @HaveFrameworkGMP@
 endif