diff --git a/src/scanner.c b/src/scanner.c
index 77ed9dc0..2fa0b318 100644
--- a/src/scanner.c
+++ b/src/scanner.c
@@ -648,7 +648,8 @@ static uint32_t column(Env *env) {
  */
 static void advance(Env *env) {
   if (not_eof(env)) {
-    array_push(&env->state->lookahead, PEEK);
+    int32_t c = PEEK;
+    array_push(&env->state->lookahead, c);
     env->lexer->advance(env->lexer, false);
   }
 }