diff --git a/.appveyor.yml b/.appveyor.yml
index d81fbb5..4e3a0af 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -28,7 +28,7 @@ init:
   - set TAG_NAME=%APPVEYOR_REPO_TAG_NAME%
 
 build_script:
-  - python ./build_scripts/append_to_version_file.py %APPVEYOR_REPO_COMMIT:~-8%
+  - python ./build_scripts/append_to_version_file.py %APPVEYOR_REPO_COMMIT:~0,8%
   - python ./build_scripts/run-clang-format.py ./src -r --clang-format-executable "C:\Program Files\LLVM\bin\clang-format.exe" --color always
   - call "build_windows.cmd"