diff --git a/vllm/Dockerfile b/vllm/Dockerfile
index dd9bdbf..3c34d8b 100644
--- a/vllm/Dockerfile
+++ b/vllm/Dockerfile
@@ -90,7 +90,11 @@ RUN mkdir -p /wheels && \
 
 FROM build-base AS build-flashinfer
 ARG FLASHINFER_ENABLE_AOT=1
-ARG FLASHINFER_REF=v0.6.7
+# flashinfer version compatibility:
+#   - v0.6.7 works with vLLM v0.18.2rc0 (Build #43)
+#   - v0.6.6 works with vLLM v0.19.0 (for Gemma 4 support)
+# ARG FLASHINFER_REF=v0.6.7  # For vLLM v0.18.2rc0
+ARG FLASHINFER_REF=v0.6.6
 ARG FLASHINFER_BUILD_SUFFIX=cu132
 ENV FLASHINFER_LOCAL_VERSION=${FLASHINFER_BUILD_SUFFIX:-}
 RUN git clone https://github.com/flashinfer-ai/flashinfer.git