diff --git a/compile.c b/compile.c
index a7308c66b1b..2ff207928a5 100644
--- a/compile.c
+++ b/compile.c
@@ -12680,7 +12680,7 @@ typedef uint32_t ibf_offset_t;
 
 #define IBF_MAJOR_VERSION ISEQ_MAJOR_VERSION
 #ifdef RUBY_DEVEL
-#define IBF_DEVEL_VERSION 7
+#define IBF_DEVEL_VERSION 8
 #define IBF_MINOR_VERSION (ISEQ_MINOR_VERSION * 10000 + IBF_DEVEL_VERSION)
 #else
 #define IBF_MINOR_VERSION ISEQ_MINOR_VERSION
@@ -13774,7 +13774,6 @@ ibf_dump_iseq_each(struct ibf_dump *dump, const rb_iseq_t *iseq)
     const struct rb_iseq_constant_body *body = ISEQ_BODY(iseq);
 
     const VALUE location_pathobj_index = ibf_dump_object(dump, body->location.pathobj); /* TODO: freeze */
-    const VALUE location_base_label_index = ibf_dump_object(dump, body->location.base_label);
     const VALUE location_label_index = ibf_dump_object(dump, body->location.label);
 
 #if IBF_ISEQ_ENABLE_LOCAL_BUFFER
@@ -13856,7 +13855,6 @@ ibf_dump_iseq_each(struct ibf_dump *dump, const rb_iseq_t *iseq)
     ibf_dump_write_small_value(dump, IBF_BODY_OFFSET(param_opt_table_offset));
     ibf_dump_write_small_value(dump, param_keyword_offset);
     ibf_dump_write_small_value(dump, location_pathobj_index);
-    ibf_dump_write_small_value(dump, location_base_label_index);
     ibf_dump_write_small_value(dump, location_label_index);
     ibf_dump_write_small_value(dump, body->location.first_lineno);
     ibf_dump_write_small_value(dump, body->location.node_id);
@@ -13972,7 +13970,6 @@ ibf_load_iseq_each(struct ibf_load *load, rb_iseq_t *iseq, ibf_offset_t offset)
     const ibf_offset_t param_opt_table_offset = (ibf_offset_t)IBF_BODY_OFFSET(ibf_load_small_value(load, &reading_pos));
     const ibf_offset_t param_keyword_offset = (ibf_offset_t)ibf_load_small_value(load, &reading_pos);
     const VALUE location_pathobj_index = ibf_load_small_value(load, &reading_pos);
-    const VALUE location_base_label_index = ibf_load_small_value(load, &reading_pos);
     const VALUE location_label_index = ibf_load_small_value(load, &reading_pos);
     const int location_first_lineno = (int)ibf_load_small_value(load, &reading_pos);
     const int location_node_id = (int)ibf_load_small_value(load, &reading_pos);
@@ -14137,7 +14134,6 @@ ibf_load_iseq_each(struct ibf_load *load, rb_iseq_t *iseq, ibf_offset_t offset)
     load->current_buffer = &load->global_buffer;
 #endif
 
-    RB_OBJ_WRITE(iseq, &load_body->location.base_label,    ibf_load_location_str(load, location_base_label_index));
     RB_OBJ_WRITE(iseq, &load_body->location.label,         ibf_load_location_str(load, location_label_index));
 
 #if IBF_ISEQ_ENABLE_LOCAL_BUFFER
diff --git a/iseq.c b/iseq.c
index 4cffe90f4d5..d88ade75866 100644
--- a/iseq.c
+++ b/iseq.c
@@ -415,7 +415,6 @@ rb_iseq_mark_and_move(rb_iseq_t *iseq, bool reference_updating)
         struct rb_iseq_variable *v = ISEQ_VARIABLE(iseq);
         if (v) rb_gc_mark_and_move(&v->script_lines);
         rb_gc_mark_and_move(&body->location.label);
-        rb_gc_mark_and_move(&body->location.base_label);
         rb_gc_mark_and_move(&body->location.pathobj);
         if (body->local_iseq) rb_gc_mark_and_move_ptr(&body->local_iseq);
         if (body->parent_iseq) rb_gc_mark_and_move_ptr(&body->parent_iseq);
@@ -711,7 +710,6 @@ iseq_location_setup(rb_iseq_t *iseq, VALUE name, VALUE path, VALUE realpath, int
 
     rb_iseq_pathobj_set(iseq, path, realpath);
     RB_OBJ_WRITE(iseq, &loc->label, name);
-    RB_OBJ_WRITE(iseq, &loc->base_label, name);
     loc->first_lineno = first_lineno;
 
     if (ISEQ_BODY(iseq)->local_iseq == iseq && rb_streql_lit(name, "initialize")) {
@@ -803,9 +801,6 @@ prepare_iseq_build(rb_iseq_t *iseq,
 
     name = rb_fstring(name);
     iseq_location_setup(iseq, name, path, realpath, first_lineno, code_location, node_id);
-    if (iseq != body->local_iseq) {
-        RB_OBJ_WRITE(iseq, &body->location.base_label, ISEQ_BODY(body->local_iseq)->location.label);
-    }
     ISEQ_ORIGINAL_ISEQ_CLEAR(iseq);
     if (body->variable) {
         body->variable->flip_count = 0;
@@ -1619,7 +1614,15 @@ rb_iseq_label(const rb_iseq_t *iseq)
 VALUE
 rb_iseq_base_label(const rb_iseq_t *iseq)
 {
-    return ISEQ_BODY(iseq)->location.base_label;
+    const struct rb_iseq_constant_body *body = ISEQ_BODY(iseq);
+    const rb_iseq_t *local_iseq = body->local_iseq;
+
+    if (local_iseq == NULL || local_iseq == iseq) {
+        return body->location.label;
+    }
+    else {
+        return ISEQ_BODY(rb_iseq_check(local_iseq))->location.label;
+    }
 }
 
 VALUE
@@ -1634,7 +1637,7 @@ rb_iseq_method_name(const rb_iseq_t *iseq)
     struct rb_iseq_constant_body *const body = ISEQ_BODY(ISEQ_BODY(iseq)->local_iseq);
 
     if (body->type == ISEQ_TYPE_METHOD) {
-        return body->location.base_label;
+        return body->location.label;
     }
     else {
         return Qnil;
diff --git a/vm_backtrace.c b/vm_backtrace.c
index f13d4273179..19bcd7dc72a 100644
--- a/vm_backtrace.c
+++ b/vm_backtrace.c
@@ -374,7 +374,7 @@ location_base_label(rb_backtrace_location_t *loc)
         return rb_id2str(loc->cme->def->original_id);
     }
 
-    return ISEQ_BODY(loc->iseq)->location.base_label;
+    return rb_iseq_base_label(loc->iseq);
 }
 
 /*
diff --git a/vm_core.h b/vm_core.h
index 2c416859573..fc64d278c65 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -338,7 +338,6 @@ struct rb_execution_context_struct;
 
 typedef struct rb_iseq_location_struct {
     VALUE pathobj;      /* String (path) or Array [path, realpath]. Frozen. */
-    VALUE base_label;   /* String */
     VALUE label;        /* String */
     int first_lineno;
     int node_id;
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index bc8b327e35b..3a0b7324046 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -3160,7 +3160,7 @@ warn_unused_block(const rb_callable_method_entry_t *cme, const rb_iseq_t *iseq,
     }
     else if (RTEST(ruby_verbose) || strict_unused_block) {
         VALUE m_loc = rb_method_entry_location((const rb_method_entry_t *)cme);
-        VALUE name = rb_gen_method_name(cme->defined_class, ISEQ_BODY(iseq)->location.base_label);
+        VALUE name = rb_gen_method_name(cme->defined_class, rb_iseq_base_label(iseq));
 
         if (!NIL_P(m_loc)) {
             rb_warn("the block passed to '%"PRIsVALUE"' defined at %"PRIsVALUE":%"PRIsVALUE" may be ignored",
diff --git a/zjit/src/cruby_bindings.inc.rs b/zjit/src/cruby_bindings.inc.rs
index 9e2946ea403..0821ed934d5 100644
--- a/zjit/src/cruby_bindings.inc.rs
+++ b/zjit/src/cruby_bindings.inc.rs
@@ -619,7 +619,6 @@ pub struct iseq_inline_storage_entry {
 #[repr(C)]
 pub struct rb_iseq_location_struct {
     pub pathobj: VALUE,
-    pub base_label: VALUE,
     pub label: VALUE,
     pub first_lineno: ::std::os::raw::c_int,
     pub node_id: ::std::os::raw::c_int,
@@ -2099,7 +2098,7 @@ pub struct zjit_jit_frame {
     pub stack: __IncompleteArrayField<VALUE>,
 }
 pub const ISEQ_BODY_OFFSET_PARAM: zjit_struct_offsets = 16;
-pub const ISEQ_BODY_OFFSET_OUTER_VARIABLES: zjit_struct_offsets = 248;
+pub const ISEQ_BODY_OFFSET_OUTER_VARIABLES: zjit_struct_offsets = 240;
 pub const RUBY_OFFSET_THREAD_RACTOR: zjit_struct_offsets = 24;
 pub type zjit_struct_offsets = u32;
 #[repr(C)]