diff --git a/src/vm.c b/src/vm.c
index 50d784fcd..e77dd1eb2 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -2178,6 +2178,7 @@ RETRY_TRY_BLOCK:
     CASE(OP_STRCAT) {
       /* A B    R(A).concat(R(B)) */
       mrb_str_concat(mrb, regs[GETARG_A(i)], regs[GETARG_B(i)]);
+      regs = mrb->c->stack;
       NEXT;
     }