diff --git a/ext/objspace/objspace.c b/ext/objspace/objspace.c
index ee76367b44..d1ccb51094 100644
--- a/ext/objspace/objspace.c
+++ b/ext/objspace/objspace.c
@@ -468,7 +468,6 @@ count_nodes(int argc, VALUE *argv, VALUE os)
 		COUNT_NODE(NODE_ERRINFO);
 		COUNT_NODE(NODE_DEFINED);
 		COUNT_NODE(NODE_POSTEXE);
-		COUNT_NODE(NODE_ALLOCA);
 		COUNT_NODE(NODE_BMETHOD);
 		COUNT_NODE(NODE_DSYM);
 		COUNT_NODE(NODE_ATTRASGN);
@@ -626,6 +625,7 @@ count_imemo_objects(int argc, VALUE *argv, VALUE self)
 	imemo_type_ids[5] = rb_intern("imemo_memo");
 	imemo_type_ids[6] = rb_intern("imemo_ment");
 	imemo_type_ids[7] = rb_intern("imemo_iseq");
+	imemo_type_ids[8] = rb_intern("imemo_alloc");
     }
 
     rb_objspace_each_objects(count_imemo_objects_i, (void *)hash);
diff --git a/gc.c b/gc.c
index a0f7e89448..bcd48565c4 100644
--- a/gc.c
+++ b/gc.c
@@ -439,6 +439,7 @@ typedef struct RVALUE {
 	    struct rb_method_entry_struct ment;
 	    const rb_iseq_t iseq;
 	    rb_env_t env;
+	    struct rb_imemo_alloc_struct alloc;
 	} imemo;
 	struct {
 	    struct RBasic basic;
@@ -2354,6 +2355,9 @@ obj_free(rb_objspace_t *objspace, VALUE obj)
 	    GC_ASSERT(VM_ENV_ESCAPED_P(RANY(obj)->as.imemo.env.ep));
 	    xfree((VALUE *)RANY(obj)->as.imemo.env.env);
 	    break;
+	  case imemo_alloc:
+	    xfree(RANY(obj)->as.imemo.alloc.ptr);
+	    break;
 	  default:
 	    break;
 	}
@@ -3282,6 +3286,9 @@ obj_memsize_of(VALUE obj, int use_all_types)
       case T_RATIONAL:
       case T_COMPLEX:
       case T_IMEMO:
+	if (imemo_type_p(obj, imemo_alloc)) {
+	    size += RANY(obj)->as.imemo.alloc.cnt * sizeof(VALUE);
+	}
 	break;
 
       case T_FLOAT:
@@ -4524,6 +4531,11 @@ gc_mark_imemo(rb_objspace_t *objspace, VALUE obj)
       case imemo_iseq:
 	rb_iseq_mark((rb_iseq_t *)obj);
 	return;
+      case imemo_alloc:
+	rb_gc_mark_locations(RANY(obj)->as.imemo.alloc.ptr,
+			     RANY(obj)->as.imemo.alloc.ptr + RANY(obj)->as.imemo.alloc.cnt);
+	rb_gc_mark(RANY(obj)->as.imemo.alloc.next);
+	return;
 #if VM_CHECK_MODE > 0
       default:
 	VM_UNREACHABLE(gc_mark_imemo);
@@ -8104,14 +8116,16 @@ ruby_mimfree(void *ptr)
 void *
 rb_alloc_tmp_buffer_with_count(volatile VALUE *store, size_t size, size_t cnt)
 {
-    NODE *s;
+    VALUE s;
+    rb_imemo_alloc_t *a;
     void *ptr;
 
-    s = rb_node_newnode(NODE_ALLOCA, 0, 0, 0);
+    s = rb_imemo_new(imemo_alloc, 0, 0, 0, 0);
     ptr = ruby_xmalloc0(size);
-    s->u1.value = (VALUE)ptr;
-    s->u3.cnt = cnt;
-    *store = (VALUE)s;
+    a = (rb_imemo_alloc_t*)s;
+    a->ptr = (VALUE*)ptr;
+    a->cnt = cnt;
+    *store = s;
     return ptr;
 }
 
@@ -9360,6 +9374,7 @@ rb_raw_obj_info(char *buff, const int buff_size, VALUE obj)
 		  IMEMO_NAME(memo);
 		  IMEMO_NAME(ment);
 		  IMEMO_NAME(iseq);
+		  IMEMO_NAME(alloc);
 #undef IMEMO_NAME
 	      }
 	      snprintf(buff, buff_size, "%s %s", buff, imemo_name);
diff --git a/internal.h b/internal.h
index 4ac024d9af..b3d3463895 100644
--- a/internal.h
+++ b/internal.h
@@ -844,7 +844,8 @@ enum imemo_type {
     imemo_memo       = 5,
     imemo_ment       = 6,
     imemo_iseq       = 7,
-    imemo_mask       = 0x07
+    imemo_alloc      = 8,
+    imemo_mask       = 0x0f
 };
 
 static inline enum imemo_type
@@ -869,12 +870,12 @@ imemo_type_p(VALUE imemo, enum imemo_type imemo_type)
 }
 
 /* FL_USER0 to FL_USER2 is for type */
-#define IMEMO_FL_USHIFT (FL_USHIFT + 3)
-#define IMEMO_FL_USER0 FL_USER3
-#define IMEMO_FL_USER1 FL_USER4
-#define IMEMO_FL_USER2 FL_USER5
-#define IMEMO_FL_USER3 FL_USER6
-#define IMEMO_FL_USER4 FL_USER7
+#define IMEMO_FL_USHIFT (FL_USHIFT + 4)
+#define IMEMO_FL_USER0 FL_USER4
+#define IMEMO_FL_USER1 FL_USER5
+#define IMEMO_FL_USER2 FL_USER6
+#define IMEMO_FL_USER3 FL_USER7
+#define IMEMO_FL_USER4 FL_USER8
 
 /* CREF in method.h */
 
@@ -929,6 +930,14 @@ rb_vm_ifunc_proc_new(VALUE (*func)(ANYARGS), const void *data)
     return rb_vm_ifunc_new(func, data, 0, UNLIMITED_ARGUMENTS);
 }
 
+typedef struct rb_imemo_alloc_struct {
+    VALUE flags;
+    VALUE reserved;
+    VALUE *ptr; /* malloc'ed buffer */
+    VALUE next; /* next imemo */
+    size_t cnt; /* buffer size in VALUE */
+} rb_imemo_alloc_t;
+
 /* MEMO */
 
 struct MEMO {
diff --git a/node.c b/node.c
index 58732ab987..c0ca3a8186 100644
--- a/node.c
+++ b/node.c
@@ -1039,7 +1039,6 @@ dump_node(VALUE buf, VALUE indent, int comment, NODE *node)
       case NODE_ARGS_AUX:
       case NODE_TO_ARY:
       case NODE_BLOCK_ARG:
-      case NODE_ALLOCA:
       case NODE_BMETHOD:
       case NODE_LAST:
 	break;
@@ -1075,9 +1074,6 @@ rb_gc_free_node(VALUE obj)
 	    xfree(RNODE(obj)->nd_ainfo);
 	}
 	break;
-      case NODE_ALLOCA:
-	xfree(RNODE(obj)->u1.node);
-	break;
     }
 }
 
@@ -1096,9 +1092,6 @@ rb_node_memsize(VALUE obj)
 	    size += sizeof(*RNODE(obj)->nd_ainfo);
 	}
 	break;
-      case NODE_ALLOCA:
-	size += RNODE(obj)->nd_cnt * sizeof(VALUE);
-	break;
     }
     return size;
 }
@@ -1223,11 +1216,6 @@ rb_gc_mark_node(NODE *obj)
       case NODE_ERRINFO:
       case NODE_BLOCK_ARG:
 	break;
-      case NODE_ALLOCA:
-	rb_gc_mark_locations((VALUE*)RNODE(obj)->u1.value,
-			     (VALUE*)RNODE(obj)->u1.value + RNODE(obj)->u3.cnt);
-	rb_gc_mark(RNODE(obj)->u2.value);
-	break;
 
       default:		/* unlisted NODE */
 	rb_gc_mark_maybe(RNODE(obj)->u1.value);
diff --git a/node.h b/node.h
index 36d83f0265..51aa5f1f23 100644
--- a/node.h
+++ b/node.h
@@ -220,8 +220,6 @@ enum node_type {
 #define NODE_DEFINED     NODE_DEFINED
     NODE_POSTEXE,
 #define NODE_POSTEXE     NODE_POSTEXE
-    NODE_ALLOCA,
-#define NODE_ALLOCA      NODE_ALLOCA
     NODE_BMETHOD,
 #define NODE_BMETHOD     NODE_BMETHOD
     NODE_DSYM,
diff --git a/parse.y b/parse.y
index 8d9e2288ed..838b6e00e9 100644
--- a/parse.y
+++ b/parse.y
@@ -170,7 +170,7 @@ typedef struct token_info {
                      token
 */
 struct parser_params {
-    NODE *heap;
+    rb_imemo_alloc_t *heap;
 
     YYSTYPE *lval;
 
@@ -11517,15 +11517,15 @@ rb_parser_set_yydebug(VALUE self, VALUE flag)
 #ifndef RIPPER
 #ifdef YYMALLOC
 #define HEAPCNT(n, size) ((n) * (size) / sizeof(YYSTYPE))
-#define NEWHEAP() rb_node_newnode(NODE_ALLOCA, 0, (VALUE)parser->heap, 0)
-#define ADD2HEAP(n, c, p) ((parser->heap = (n))->u1.node = (p), \
-			   (n)->u3.cnt = (c), (p))
+#define NEWHEAP() rb_imemo_new(imemo_alloc, 0, (VALUE)parser->heap, 0, 0)
+#define ADD2HEAP(n, c, p) ((parser->heap = (n))->ptr = (p), \
+			   (n)->cnt = (c), (p))
 
 void *
 rb_parser_malloc(struct parser_params *parser, size_t size)
 {
     size_t cnt = HEAPCNT(1, size);
-    NODE *n = NEWHEAP();
+    rb_imemo_alloc_t *n = NEWHEAP();
     void *ptr = xmalloc(size);
 
     return ADD2HEAP(n, cnt, ptr);
@@ -11535,7 +11535,7 @@ void *
 rb_parser_calloc(struct parser_params *parser, size_t nelem, size_t size)
 {
     size_t cnt = HEAPCNT(nelem, size);
-    NODE *n = NEWHEAP();
+    rb_imemo_alloc_t *n = NEWHEAP();
     void *ptr = xcalloc(nelem, size);
 
     return ADD2HEAP(n, cnt, ptr);
@@ -11544,17 +11544,17 @@ rb_parser_calloc(struct parser_params *parser, size_t nelem, size_t size)
 void *
 rb_parser_realloc(struct parser_params *parser, void *ptr, size_t size)
 {
-    NODE *n;
+    rb_imemo_alloc_t *n;
     size_t cnt = HEAPCNT(1, size);
 
     if (ptr && (n = parser->heap) != NULL) {
 	do {
-	    if (n->u1.node == ptr) {
-		n->u1.node = ptr = xrealloc(ptr, size);
-		if (n->u3.cnt) n->u3.cnt = cnt;
+	    if (n->ptr == ptr) {
+		n->ptr = ptr = xrealloc(ptr, size);
+		if (n->cnt) n->cnt = cnt;
 		return ptr;
 	    }
-	} while ((n = n->u2.node) != NULL);
+	} while ((n = n->next) != NULL);
     }
     n = NEWHEAP();
     ptr = xrealloc(ptr, size);
@@ -11564,15 +11564,15 @@ rb_parser_realloc(struct parser_params *parser, void *ptr, size_t size)
 void
 rb_parser_free(struct parser_params *parser, void *ptr)
 {
-    NODE **prev = &parser->heap, *n;
+    rb_imemo_alloc_t **prev = &parser->heap, *n;
 
     while ((n = *prev) != NULL) {
-	if (n->u1.node == ptr) {
-	    *prev = n->u2.node;
+	if (n->ptr == ptr) {
+	    *prev = n->next;
 	    rb_gc_force_recycle((VALUE)n);
 	    break;
 	}
-	prev = &n->u2.node;
+	prev = &n->next;
     }
     xfree(ptr);
 }