diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile b/src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile
index 17fc1a5749299..bc9d7831867e7 100644
--- a/src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile
+++ b/src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile
@@ -79,11 +79,17 @@ ENV PATH="/node/bin:${PATH}"
 COPY host-x86_64/x86_64-gnu-tools/browser-ui-test.version /tmp/
 
 ENV RUST_CONFIGURE_ARGS \
+  --set rust.debug-assertions=false \
   --build=x86_64-unknown-linux-gnu \
   --save-toolstates=/tmp/toolstate/toolstates.json \
   --enable-new-symbol-mangling
 
 ENV HOST_TARGET x86_64-unknown-linux-gnu
+
+# NOTE(jieyouxu): currently rustc alt builds do *not* have rustc debug
+# assertions enabled! Since this job apparently needs to force CI rustc, then we
+# cannot set rustc debug assertions.
+ENV NO_DEBUG_ASSERTIONS 1
 ENV FORCE_CI_RUSTC 1
 
 COPY host-x86_64/dist-x86_64-linux/shared.sh /scripts/