diff --git a/.ci/compile.sh b/.ci/compile.sh
index 8cf9bd9d7..3d9516eee 100755
--- a/.ci/compile.sh
+++ b/.ci/compile.sh
@@ -227,7 +227,7 @@ if [[ $RUNNER_OS == macOS ]]; then
     flags+=(-DCPACK_COMMAND_HDIUTIL="$hdiutil_script")
   fi
 
-elif [[ $RUNNER_OS == Windows ]]; then
+elif [[ $RUNNER_OS == Windows ]] && [[ "$CMAKE_GENERATOR" != *Ninja* ]]; then
   # Enable MTT, see https://devblogs.microsoft.com/cppblog/improved-parallelism-in-msbuild/
   # and https://devblogs.microsoft.com/cppblog/cpp-build-throughput-investigation-and-tune-up/#multitooltask-mtt
   buildflags+=(-- -p:UseMultiToolTask=true -p:EnableClServerMode=true)