diff --git a/dist-build/emscripten.sh b/dist-build/emscripten.sh
index ee06079f..86bf974f 100755
--- a/dist-build/emscripten.sh
+++ b/dist-build/emscripten.sh
@@ -17,7 +17,7 @@ export LDFLAGS="${LDFLAGS} -s NODEJS_CATCH_EXIT=0"
 export LDFLAGS="${LDFLAGS} -s NODEJS_CATCH_REJECTION=0"
 export LDFLAGS="${LDFLAGS} -s WASM_BIGINT=0"
 export LDFLAGS="${LDFLAGS} -flto"
-export CFLAGS="${CFLAGS} -flto"
+export CFLAGS="${CFLAGS:+${CFLAGS} }-flto"
 
 echo
 if [ "$1" = "--standard" ]; then