diff --git a/infra/Dockerfile.server b/infra/Dockerfile.server
index 236ab0b..4f71b73 100644
--- a/infra/Dockerfile.server
+++ b/infra/Dockerfile.server
@@ -8,8 +8,10 @@ ARG TARGETPLATFORM
 ARG TARGETARCH
 ARG TARGETVARIANT
 
-# Install cross-compilation toolchains only when actually cross-compiling.
-RUN apt-get update && apt-get install -y pkg-config && \
+# Install build tools. gcc is always needed: cc-rs (used by ring/aes-gcm deps)
+# calls the native compiler even on native builds, and rust:slim doesn't
+# include it.  Cross-compilers are added only when actually cross-compiling.
+RUN apt-get update && apt-get install -y gcc pkg-config && \
     if [ "${BUILDPLATFORM}" != "${TARGETPLATFORM}" ]; then \
       case "${TARGETARCH}:${TARGETVARIANT}" in \
         "arm64:")  apt-get install -y gcc-aarch64-linux-gnu    ;; \
@@ -29,8 +31,13 @@ RUN case "${TARGETARCH}:${TARGETVARIANT}" in \
     esac > /rust_target && \
     rustup target add "$(cat /rust_target)"
 
-# Tell Cargo which cross-linker to use (ignored on native builds).
+# Tell Cargo which linker to use for each target.
+# x86_64 native: use plain gcc (cc-rs would otherwise look for
+# "x86_64-linux-gnu-gcc" which is the *cross* toolchain, not installed here).
 RUN mkdir -p /root/.cargo && printf '\
+[target.x86_64-unknown-linux-gnu]\n\
+linker = "gcc"\n\
+\n\
 [target.aarch64-unknown-linux-gnu]\n\
 linker = "aarch64-linux-gnu-gcc"\n\
 \n\