[appveyor] fix syntax

diff --git a/appveyor.yml b/appveyor.yml
index 10fc3b8..15661ee 100644 (file)
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -24,7 +24,7 @@ skip_commits:
   message: /\[av skip\]/
 
 cache:
-  - %APPVEYOR_BUILD_FOLDER%\build
+  - '%APPVEYOR_BUILD_FOLDER%\build'
 
 environment:
   global: