diff --git a/.github/workflows/compilers.yml b/.github/workflows/compilers.yml
index e3d68b018f..1aba46569f 100644
--- a/.github/workflows/compilers.yml
+++ b/.github/workflows/compilers.yml
@@ -165,7 +165,6 @@ jobs:
 #         - { name: SYMBOL_DEBUG,                   env: { cppflags: '-DSYMBOL_DEBUG' } }
 
 #         - { name: RGENGC_CHECK_MODE,              env: { cppflags: '-DRGENGC_CHECK_MODE' } }
-#         - { name: TRANSIENT_HEAP_CHECK_MODE,      env: { cppflags: '-DTRANSIENT_HEAP_CHECK_MODE' } }
 #         - { name: VM_CHECK_MODE,                  env: { cppflags: '-DVM_CHECK_MODE' } }
 
 #         - { name: USE_EMBED_CI=0,                 env: { cppflags: '-DUSE_EMBED_CI=0' } }
diff --git a/array.c b/array.c
index 82ba8dc741..c216c05d61 100644
--- a/array.c
+++ b/array.c
@@ -57,8 +57,6 @@ VALUE rb_cArray;
  *                they cannot be modified. Not updating the reference count
  *                improves copy-on-write performance. Their reference count is
  *                assumed to be infinity.
- * 13:  RARRAY_TRANSIENT_FLAG
- *          The buffer of the array is allocated on the transient heap.
  * 14:  RARRAY_PTR_IN_USE_FLAG
  *          The buffer of the array is in use. This is only used during
  *          debugging.
@@ -387,7 +385,6 @@ rb_ary_make_embedded(VALUE ary)
         const VALUE *buf = ARY_HEAP_PTR(ary);
         long len = ARY_HEAP_LEN(ary);
 
-        // FL_SET_EMBED also unsets the transient flag
         FL_SET_EMBED(ary);
         ARY_SET_EMBED_LEN(ary, len);
 
diff --git a/debug_counter.h b/debug_counter.h
index 910f6ebf41..01b1a63f86 100644
--- a/debug_counter.h
+++ b/debug_counter.h
@@ -207,7 +207,6 @@ RB_DEBUG_COUNTER(gc_isptr_maybe)
  * * [attr]
  *   * _ptr: R?? is not embed.
  *   * _embed: R?? is embed.
- *   * _transient: R?? uses transient heap.
  * * type specific attr.
  *   * str_shared: str is shared.
  *   * str_nofree:        nofree
diff --git a/internal/struct.h b/internal/struct.h
index 00158c87d9..6da5bad10a 100644
--- a/internal/struct.h
+++ b/internal/struct.h
@@ -15,7 +15,6 @@ enum {
     RSTRUCT_EMBED_LEN_MASK = RUBY_FL_USER7 | RUBY_FL_USER6 | RUBY_FL_USER5 | RUBY_FL_USER4 |
                                  RUBY_FL_USER3 | RUBY_FL_USER2 | RUBY_FL_USER1,
     RSTRUCT_EMBED_LEN_SHIFT = (RUBY_FL_USHIFT+1),
-    RSTRUCT_TRANSIENT_FLAG = RUBY_FL_USER8,
 };
 
 struct RStruct {
diff --git a/internal/variable.h b/internal/variable.h
index ed622cd905..c467489b77 100644
--- a/internal/variable.h
+++ b/internal/variable.h
@@ -15,10 +15,6 @@
 #include "ruby/ruby.h"          /* for VALUE */
 #include "shape.h"              /* for rb_shape_t */
 
-/* global variable */
-
-#define ROBJECT_TRANSIENT_FLAG    FL_USER2
-
 /* variable.c */
 void rb_gc_mark_global_tbl(void);
 void rb_gc_update_global_tbl(void);