diff --git a/benchmark/vm_ivar_init.yml b/benchmark/vm_ivar_init.yml
new file mode 100644
index 0000000000..c6f1633907
--- /dev/null
+++ b/benchmark/vm_ivar_init.yml
@@ -0,0 +1,14 @@
+prelude: |
+  class C
+    def initialize
+      @a = nil
+      @b = nil
+      @c = nil
+      @d = nil
+      @e = nil
+    end
+  end
+benchmark:
+  vm_ivar_init: |
+    C.new
+loop_count: 30000000
diff --git a/internal/variable.h b/internal/variable.h
index d5d0cccbfb..34ad4e1199 100644
--- a/internal/variable.h
+++ b/internal/variable.h
@@ -52,6 +52,7 @@ VALUE rb_gvar_get(ID);
 VALUE rb_gvar_set(ID, VALUE);
 VALUE rb_gvar_defined(ID);
 void rb_const_warn_if_deprecated(const rb_const_entry_t *, VALUE, ID);
+void rb_init_iv_list(VALUE obj, uint32_t len, uint32_t newsize, st_table * index_tbl);
 MJIT_SYMBOL_EXPORT_END
 
 static inline bool
diff --git a/variable.c b/variable.c
index 7ebbcf85b8..669d47e8d3 100644
--- a/variable.c
+++ b/variable.c
@@ -1402,6 +1402,28 @@ rb_obj_transient_heap_evacuate(VALUE obj, int promote)
 }
 #endif
 
+void
+rb_init_iv_list(VALUE obj, uint32_t len, uint32_t newsize, st_table * index_tbl)
+{
+    VALUE *ptr = ROBJECT_IVPTR(obj);
+    VALUE *newptr;
+
+    if (RBASIC(obj)->flags & ROBJECT_EMBED) {
+        newptr = obj_ivar_heap_alloc(obj, newsize);
+        MEMCPY(newptr, ptr, VALUE, len);
+        RBASIC(obj)->flags &= ~ROBJECT_EMBED;
+        ROBJECT(obj)->as.heap.ivptr = newptr;
+    } else {
+        newptr = obj_ivar_heap_realloc(obj, len, newsize);
+    }
+
+    for (; len < newsize; len++) {
+        newptr[len] = Qundef;
+    }
+    ROBJECT(obj)->as.heap.numiv = newsize;
+    ROBJECT(obj)->as.heap.iv_index_tbl = index_tbl;
+}
+
 static VALUE
 obj_ivar_set(VALUE obj, ID id, VALUE val)
 {
@@ -1419,25 +1441,8 @@ obj_ivar_set(VALUE obj, ID id, VALUE val)
 
     len = ROBJECT_NUMIV(obj);
     if (len <= ivup.index) {
-        VALUE *ptr = ROBJECT_IVPTR(obj);
-        VALUE *newptr;
         uint32_t newsize = iv_index_tbl_newsize(&ivup);
-
-        if (RBASIC(obj)->flags & ROBJECT_EMBED) {
-            newptr = obj_ivar_heap_alloc(obj, newsize);
-            MEMCPY(newptr, ptr, VALUE, len);
-            RBASIC(obj)->flags &= ~ROBJECT_EMBED;
-            ROBJECT(obj)->as.heap.ivptr = newptr;
-        }
-        else {
-            newptr = obj_ivar_heap_realloc(obj, len, newsize);
-        }
-
-        for (; len < newsize; len++) {
-            newptr[len] = Qundef;
-        }
-        ROBJECT(obj)->as.heap.numiv = newsize;
-        ROBJECT(obj)->as.heap.iv_index_tbl = ivup.u.iv_index_tbl;
+        rb_init_iv_list(obj, len, newsize, ivup.u.iv_index_tbl);
     }
     RB_OBJ_WRITE(obj, &ROBJECT_IVPTR(obj)[ivup.index], val);
 
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 51b3c40010..f8b2f707ca 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -1213,11 +1213,21 @@ vm_setivar(VALUE obj, ID id, VALUE val, const rb_iseq_t *iseq, IVC ic, const str
 	    VALUE *ptr = ROBJECT_IVPTR(obj);
 	    index = !is_attr ? ic->entry->index : vm_cc_attr_index(cc)-1;
 
-	    if (RB_DEBUG_COUNTER_INC_UNLESS(ivar_set_ic_miss_oorange, index < ROBJECT_NUMIV(obj))) {
+	    if (index < ROBJECT_NUMIV(obj)) {
 		RB_OBJ_WRITE(obj, &ptr[index], val);
 		RB_DEBUG_COUNTER_INC(ivar_set_ic_hit);
 		return val; /* inline cache hit */
-	    }
+	    } else {
+                st_table * iv_idx_tbl = RCLASS_IV_INDEX_TBL(rb_class_real(klass));
+                if (index < iv_idx_tbl->num_entries) {
+                    rb_init_iv_list(obj, ROBJECT_NUMIV(obj), iv_idx_tbl->num_entries, iv_idx_tbl);
+                    ptr = ROBJECT_IVPTR(obj);
+                    RB_OBJ_WRITE(obj, &ptr[index], val);
+                    RB_DEBUG_COUNTER_INC(ivar_set_ic_hit);
+                    return val; /* inline cache hit */
+                }
+            }
+            RB_DEBUG_COUNTER_INC(ivar_set_ic_miss_oorange);
 	}
 	else {
 	    struct st_table *iv_index_tbl = ROBJECT_IV_INDEX_TBL(obj);