diff --git a/.appveyor.yml b/.appveyor.yml
index f3aeb99589..015f4dd200 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -14,7 +14,7 @@ build_script:
   - bash ./tools/import-upstream.sh
   - bash -c 'cd src; ./get-clang.sh'
   - bash -c '~/.cargo/bin/sccache -s'
-  - bash -c 'cd src; EXTRA_FLAGS=target_cpu=\"$PLATFORM\" ./build.sh'
+  - bash -c 'cd src; EXTRA_FLAGS=target_cpu=\"$Platform\" ./build.sh'
   - bash -c '~/.cargo/bin/sccache -s'
   - ps: $env:BUILD_NAME="naiveproxy-$env:APPVEYOR_REPO_TAG_NAME-win-$env:PLATFORM"
   - bash -c 'mkdir $BUILD_NAME'