diff --git a/appveyor.yml b/appveyor.yml
index 24570bd..d185b09 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -36,4 +36,4 @@ install:
 build: off
 
 test_script:
-  - b2 libs/mp11/test toolset=$TOOLSET
+  - b2 libs/mp11/test toolset=%TOOLSET%