1 files changed, 3 insertions, 1 deletions
diff --git a/string.c b/string.c
index 6ab768c244..403b8df15f 100644
--- a/string.c
+++ b/string.c
@@ -485,7 +485,7 @@ build_fstring(VALUE str, struct fstr_update_arg *arg)
     RUBY_ASSERT(RB_TYPE_P(str, T_STRING));
     RUBY_ASSERT(OBJ_FROZEN(str));
     RUBY_ASSERT(!FL_TEST_RAW(str, STR_FAKESTR));
-    RUBY_ASSERT(!FL_TEST_RAW(str, FL_EXIVAR));
+    RUBY_ASSERT(!rb_obj_exivar_p(str));
     RUBY_ASSERT(RBASIC_CLASS(str) == rb_cString);
     RUBY_ASSERT(!rb_objspace_garbage_object_p(str));
 
@@ -3664,6 +3664,7 @@ RUBY_ALIAS_FUNCTION(rb_str_dup_frozen(VALUE str), rb_str_new_frozen, (str))
 VALUE
 rb_str_locktmp(VALUE str)
 {
+    rb_check_frozen(str);
     if (FL_TEST(str, STR_TMPLOCK)) {
         rb_raise(rb_eRuntimeError, "temporal locking already locked string");
     }
@@ -3674,6 +3675,7 @@ rb_str_locktmp(VALUE str)
 VALUE
 rb_str_unlocktmp(VALUE str)
 {
+    rb_check_frozen(str);
     if (!FL_TEST(str, STR_TMPLOCK)) {
         rb_raise(rb_eRuntimeError, "temporal unlocking already unlocked string");
     }