diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-gcc/Dockerfile b/src/ci/docker/host-x86_64/x86_64-gnu-gcc/Dockerfile
index 2208ed3ffbe15..fa1bb9f811452 100644
--- a/src/ci/docker/host-x86_64/x86_64-gnu-gcc/Dockerfile
+++ b/src/ci/docker/host-x86_64/x86_64-gnu-gcc/Dockerfile
@@ -51,3 +51,22 @@ ENV SCRIPT="python3 ../x.py \
   --skip tests/rustdoc-json \
   --skip tests/rustdoc-ui \
   --set rust.codegen-backends=[\\\"llvm\\\",\\\"gcc\\\"]"
+
+# Build sysroot with gcc backend and run libcore tests in stage 1.
+# We need to disable optimizations because of https://github.com/rust-lang/rustc_codegen_gcc/issues/686
+ENV RUST_CONFIGURE_ARGS="--build=x86_64-unknown-linux-gnu \
+ --enable-sanitizers \
+ --enable-profiler \
+ --enable-compiler-docs \
+ --set llvm.libzstd=true \
+ --set rust.optimize=false \
+ --set rust.optimize-tests=false \
+ --set rust.debug-assertions=false \
+ --set rust.codegen-backends=[\\\"gcc\\\"]"
+ENV SCRIPT="python3 ../x.py \
+  --stage 1 \
+  test library/core \
+ --set rust.optimize=false \
+ --set rust.optimize-tests=false \
+ --set rust.debug-assertions=false \
+ --set rust.codegen-backends=[\\\"gcc\\\"]"