diff --git a/src/lj_api.c b/src/lj_api.c
index 3bedb39f..ad17a972 100644
--- a/src/lj_api.c
+++ b/src/lj_api.c
@@ -1018,6 +1018,10 @@ LUA_API const char *lua_setupvalue(lua_State *L, int idx, int n)
   api_checknelems(L, 1);
   name = lj_debug_uvnamev(f, (uint32_t)(n-1), &val);
   if (name) {
+    /* Flush cache, as the upvalue might have PROTO_UV_IMMUTABLE set, which
+       doesn't take the debug library into account. But not during __gc. */
+    if (lj_trace_flushall(L))
+      lj_err_caller(L, LJ_ERR_NOGCMM);
     L->top--;
     copyTV(L, val, L->top);
     lj_gc_barrier(L, funcV(f), L->top);
diff --git a/src/lj_debug.c b/src/lj_debug.c
index bd2fa1f5..64757f00 100644
--- a/src/lj_debug.c
+++ b/src/lj_debug.c
@@ -13,6 +13,7 @@
 #include "lj_tab.h"
 #include "lj_state.h"
 #include "lj_frame.h"
+#include "lj_trace.h"
 #include "lj_bc.h"
 #include "lj_vm.h"
 #if LJ_HASJIT
@@ -426,8 +427,14 @@ LUA_API const char *lua_setlocal(lua_State *L, const lua_Debug *ar, int n)
 {
   const char *name = NULL;
   TValue *o = debug_localname(L, ar, &name, (BCReg)n);
-  if (name)
+  if (name) {
+    /* Flush cache, as the local might be aliased by an upvalue with
+       PROTO_UV_IMMUTABLE set, and said flag doesn't take the debug library
+       into account. But not during __gc. */
+    if (lj_trace_flushall(L))
+      lj_err_caller(L, LJ_ERR_NOGCMM);
     copyTV(L, o, L->top-1);
+  }
   L->top--;
   return name;
 }