diff --git a/appveyor.yml b/appveyor.yml
index f3a46a4d..95af229f 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -20,7 +20,7 @@ init:
 
 install:
   - cinst cmake
-  - xcopy /I third-party/vcpkg/ports/miniupnpc c:\tools\vcpkg\ports\miniupnpc
+  - xcopy /I third-party\vcpkg\ports\miniupnpc c:\tools\vcpkg\ports\miniupnpc
 
 before_build:
   - vcpkg install libiconv --triplet %PLATFORM%-windows-static