4 files changed, 14 insertions, 4 deletions
diff --git a/compile.c b/compile.c
index d3cb079562..efe90bed10 100644
--- a/compile.c
+++ b/compile.c
@@ -11554,6 +11554,7 @@ ibf_load_outer_variables(const struct ibf_load * load, ibf_offset_t outer_variab
     for (size_t i = 0; i < table_size; i++) {
         ID key = ibf_load_id(load, (ID)ibf_load_small_value(load, &reading_pos));
         VALUE value = ibf_load_small_value(load, &reading_pos);
+        if (!key) key = rb_make_temporary_id(i);
         rb_id_table_insert(tbl, key, value);
     }
 
diff --git a/internal/symbol.h b/internal/symbol.h
index 6875d98db3..4f041330f9 100644
--- a/internal/symbol.h
+++ b/internal/symbol.h
@@ -28,6 +28,7 @@ int rb_is_local_name(VALUE name);
 PUREFUNC(int rb_is_const_sym(VALUE sym));
 PUREFUNC(int rb_is_attrset_sym(VALUE sym));
 ID rb_make_internal_id(void);
+ID rb_make_temporary_id(size_t n);
 void rb_gc_free_dsymbol(VALUE);
 
 #if __has_builtin(__builtin_constant_p)
diff --git a/parse.y b/parse.y
index d386561f6a..29517daa20 100644
--- a/parse.y
+++ b/parse.y
@@ -13090,10 +13090,7 @@ rb_init_parse(void)
 static ID
 internal_id(struct parser_params *p)
 {
-    const ID max_id = RB_ID_SERIAL_MAX & ~0xffff;
-    ID id = (ID)vtable_size(p->lvtbl->args) + (ID)vtable_size(p->lvtbl->vars);
-    id = max_id - id;
-    return ID_STATIC_SYM | ID_INTERNAL | (id << ID_SCOPE_SHIFT);
+    return rb_make_temporary_id(vtable_size(p->lvtbl->args) + vtable_size(p->lvtbl->vars));
 }
 #endif /* !RIPPER */
 
diff --git a/symbol.c b/symbol.c
index 79ec4de502..5ce95f5b07 100644
--- a/symbol.c
+++ b/symbol.c
@@ -952,6 +952,17 @@ rb_make_internal_id(void)
     return next_id_base() | ID_INTERNAL | ID_STATIC_SYM;
 }
 
+ID
+rb_make_temporary_id(size_t n)
+{
+    const ID max_id = RB_ID_SERIAL_MAX & ~0xffff;
+    const ID id = max_id - (ID)n;
+    if (id <= ruby_global_symbols.last_id) {
+	rb_raise(rb_eRuntimeError, "too big to make temporary ID: %" PRIdSIZE, n);
+    }
+    return (id << ID_SCOPE_SHIFT) | ID_STATIC_SYM | ID_INTERNAL;
+}
+
 static int
 symbols_i(st_data_t key, st_data_t value, st_data_t arg)
 {