diff --git a/appveyor.yml b/appveyor.yml
index 44421566..877383b5 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -28,7 +28,7 @@ before_build:
         $env:PATH = $env:PATH -replace "C:\\Program Files \(x86\)\\Git\\bin",""
         $generator = "-GMinGW Makefiles"
       }
-      cmake -DFMT_EXTRA_TESTS=ON -DCMAKE_BUILD_TYPE=$env:Configuration "$generator" .
+      cmake -DFMT_EXTRA_TESTS=ON "-DCMAKE_BUILD_TYPE=$env:Configuration" "$generator" .
 
 build_script:
   - ps: |