diff --git a/Cross.toml b/Cross.toml
index 2a7689e..897692b 100644
--- a/Cross.toml
+++ b/Cross.toml
@@ -1,2 +1,16 @@
 [build.env]
 passthrough = ["JEMALLOC_SYS_WITH_LG_PAGE"]
+
+# The default x86_64-unknown-linux-gnu cross image (Ubuntu 20.04) ships GCC 9.x,
+# which is affected by https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95189 (a memcmp
+# miscompilation). aws-lc-sys >= 0.33 hard-panics with "### COMPILER BUG DETECTED ###"
+# when it finds this compiler, breaking the build. Install GCC 10 (10.3.0, in the
+# "known to work" set) and point gcc/g++/cc at it so every C dependency builds with it.
+# aarch64 is unaffected: it's a true cross-compile, so aws-lc-sys can't run its probe
+# binary and skips the check entirely.
+[target.x86_64-unknown-linux-gnu]
+pre-build = [
+    "apt-get update && apt-get install --assume-yes gcc-10 g++-10",
+    "update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-10 100 --slave /usr/bin/g++ g++ /usr/bin/g++-10",
+    "update-alternatives --install /usr/bin/cc cc /usr/bin/gcc-10 100",
+]