diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a86cda9a7..f03fc5008 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -595,6 +595,7 @@ jobs:
             openexr_ver: v3.3.2
             openimageio_ver: release
             setenvs: export LLVM_VERSION=18.1.8
+                            OSL_CMAKE_FLAGS="-DUSE_LLVM_BTCODE=ON"
           - desc: Windows-2022 VS2022
             runner: windows-2022
             nametag: windows-2022
@@ -607,4 +608,5 @@ jobs:
             openexr_ver: v3.3.2
             openimageio_ver: release
             setenvs: export LLVM_VERSION=18.1.8
+                            OSL_CMAKE_FLAGS="-DUSE_LLVM_BTCODE=ON"
             # setenvs: export LLVM_VERSION=19.1.5