diff --git a/ChangeLog b/ChangeLog
index 523a8dc0dd..8c55c0355c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+Sat Nov  9 12:45:00 2013  Charlie Somerville  <charliesome@ruby-lang.org>
+
+	* insns.def: unify ic_constant_serial and ic_class_serial into one field
+	  ic_serial. This is possible because these fields are only ever used
+	  exclusively with each other.
+
+	* insns.def: ditto
+	* vm_core.h: ditto
+	* vm_insnhelper.c: ditto
+
 Sat Nov  9 12:31:00 2013  Charlie Somerville  <charliesome@ruby-lang.org>
 
 	* class.c: unify names of vm state version counters to 'serial'.
diff --git a/insns.def b/insns.def
index 402371e288..6075d98db2 100644
--- a/insns.def
+++ b/insns.def
@@ -1183,7 +1183,7 @@ getinlinecache
 ()
 (VALUE val)
 {
-    if (ic->ic_constant_serial == GET_CONSTANT_SERIAL()) {
+    if (ic->ic_serial == GET_CONSTANT_SERIAL()) {
 	val = ic->ic_value.value;
 	JUMP(dst);
     }
@@ -1208,7 +1208,7 @@ setinlinecache
 	rb_iseq_add_mark_object(GET_ISEQ(), val);
     }
     ic->ic_value.value = val;
-    ic->ic_constant_serial = GET_CONSTANT_SERIAL() - ruby_vm_const_missing_count;
+    ic->ic_serial = GET_CONSTANT_SERIAL() - ruby_vm_const_missing_count;
     ruby_vm_const_missing_count = 0;
 }
 
diff --git a/vm_core.h b/vm_core.h
index 4bb5cc2976..44f871dd6f 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -131,8 +131,7 @@ typedef struct rb_compile_option_struct rb_compile_option_t;
 
 
 struct iseq_inline_cache_entry {
-    rb_serial_t ic_constant_serial;
-    rb_serial_t ic_class_serial;
+    rb_serial_t ic_serial;
     union {
 	size_t index;
 	VALUE value;
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 20f7af896d..9844d47689 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -510,7 +510,7 @@ vm_getivar(VALUE obj, ID id, IC ic, rb_call_info_t *ci, int is_attr)
 	VALUE val = Qundef;
 	VALUE klass = RBASIC(obj)->klass;
 
-	if (LIKELY((!is_attr && ic->ic_class_serial == RCLASS_EXT(klass)->class_serial) ||
+	if (LIKELY((!is_attr && ic->ic_serial == RCLASS_EXT(klass)->class_serial) ||
 		   (is_attr && ci->aux.index > 0))) {
 	    long index = !is_attr ? (long)ic->ic_value.index : ci->aux.index - 1;
 	    long len = ROBJECT_NUMIV(obj);
@@ -533,7 +533,7 @@ vm_getivar(VALUE obj, ID id, IC ic, rb_call_info_t *ci, int is_attr)
 		    }
 		    if (!is_attr) {
 			ic->ic_value.index = index;
-			ic->ic_class_serial = RCLASS_EXT(klass)->class_serial;
+			ic->ic_serial = RCLASS_EXT(klass)->class_serial;
 		    }
 		    else { /* call_info */
 			ci->aux.index = index + 1;
@@ -565,7 +565,7 @@ vm_setivar(VALUE obj, ID id, VALUE val, IC ic, rb_call_info_t *ci, int is_attr)
 	st_data_t index;
 
 	if (LIKELY(
-	    (!is_attr && ic->ic_class_serial == RCLASS_EXT(klass)->class_serial) ||
+	    (!is_attr && ic->ic_serial == RCLASS_EXT(klass)->class_serial) ||
 	    (is_attr && ci->aux.index > 0))) {
 	    long index = !is_attr ? (long)ic->ic_value.index : ci->aux.index-1;
 	    long len = ROBJECT_NUMIV(obj);
@@ -582,7 +582,7 @@ vm_setivar(VALUE obj, ID id, VALUE val, IC ic, rb_call_info_t *ci, int is_attr)
 	    if (iv_index_tbl && st_lookup(iv_index_tbl, (st_data_t)id, &index)) {
 		if (!is_attr) {
 		    ic->ic_value.index = index;
-		    ic->ic_class_serial = RCLASS_EXT(klass)->class_serial;
+		    ic->ic_serial = RCLASS_EXT(klass)->class_serial;
 		}
 		else {
 		    ci->aux.index = index + 1;