diff --git a/common/build-helper/rust.sh b/common/build-helper/rust.sh
index 6fcd3bd7d9..431cb5f0fd 100644
--- a/common/build-helper/rust.sh
+++ b/common/build-helper/rust.sh
@@ -17,6 +17,12 @@ if [ "$CROSS_BUILD" ]; then
 	# [build]
 	# target = ${RUST_TARGET}
 	export CARGO_BUILD_TARGET="$RUST_TARGET"
+
+	# If cc-rs needs to build host binaries, it guesses the compiler and
+	# uses default (wrong) flags unless they are specified explicitly;
+	# innocuous flags are used here just to disable its defaults
+	export HOST_CC="gcc"
+	export HOST_CFLAGS="-O2"
 else
 	unset CARGO_BUILD_TARGET
 fi