diff --git a/alloc.c b/alloc.c
index eb22a45c9d..12afadfacd 100644
--- a/alloc.c
+++ b/alloc.c
@@ -18,25 +18,6 @@
 
 #define BLOCKING 1024
 
-#define DEFINE_ALLOCATOR(name, type)				\
-static unsigned int name##_allocs;				\
-void *alloc_##name##_node(void)					\
-{								\
-	static int nr;						\
-	static type *block;					\
-	void *ret;						\
-								\
-	if (!nr) {						\
-		nr = BLOCKING;					\
-		block = xmalloc(BLOCKING * sizeof(type));	\
-	}							\
-	nr--;							\
-	name##_allocs++;					\
-	ret = block++;						\
-	memset(ret, 0, sizeof(type));				\
-	return ret;						\
-}
-
 union any_object {
 	struct object object;
 	struct blob blob;
@@ -45,17 +26,73 @@ union any_object {
 	struct tag tag;
 };
 
-DEFINE_ALLOCATOR(blob, struct blob)
-DEFINE_ALLOCATOR(tree, struct tree)
-DEFINE_ALLOCATOR(raw_commit, struct commit)
-DEFINE_ALLOCATOR(tag, struct tag)
-DEFINE_ALLOCATOR(object, union any_object)
+struct alloc_state {
+	int count; /* total number of nodes allocated */
+	int nr;    /* number of nodes left in current allocation */
+	void *p;   /* first free node in current allocation */
+};
+
+static inline void *alloc_node(struct alloc_state *s, size_t node_size)
+{
+	void *ret;
+
+	if (!s->nr) {
+		s->nr = BLOCKING;
+		s->p = xmalloc(BLOCKING * node_size);
+	}
+	s->nr--;
+	s->count++;
+	ret = s->p;
+	s->p = (char *)s->p + node_size;
+	memset(ret, 0, node_size);
+	return ret;
+}
+
+static struct alloc_state blob_state;
+void *alloc_blob_node(void)
+{
+	struct blob *b = alloc_node(&blob_state, sizeof(struct blob));
+	b->object.type = OBJ_BLOB;
+	return b;
+}
+
+static struct alloc_state tree_state;
+void *alloc_tree_node(void)
+{
+	struct tree *t = alloc_node(&tree_state, sizeof(struct tree));
+	t->object.type = OBJ_TREE;
+	return t;
+}
+
+static struct alloc_state tag_state;
+void *alloc_tag_node(void)
+{
+	struct tag *t = alloc_node(&tag_state, sizeof(struct tag));
+	t->object.type = OBJ_TAG;
+	return t;
+}
+
+static struct alloc_state object_state;
+void *alloc_object_node(void)
+{
+	struct object *obj = alloc_node(&object_state, sizeof(union any_object));
+	obj->type = OBJ_NONE;
+	return obj;
+}
+
+static struct alloc_state commit_state;
+
+unsigned int alloc_commit_index(void)
+{
+	static unsigned int count;
+	return count++;
+}
 
 void *alloc_commit_node(void)
 {
-	static int commit_count;
-	struct commit *c = alloc_raw_commit_node();
-	c->index = commit_count++;
+	struct commit *c = alloc_node(&commit_state, sizeof(struct commit));
+	c->object.type = OBJ_COMMIT;
+	c->index = alloc_commit_index();
 	return c;
 }
 
@@ -66,13 +103,13 @@ static void report(const char *name, unsigned int count, size_t size)
 }
 
 #define REPORT(name, type)	\
-    report(#name, name##_allocs, name##_allocs * sizeof(type) >> 10)
+    report(#name, name##_state.count, name##_state.count * sizeof(type) >> 10)
 
 void alloc_report(void)
 {
 	REPORT(blob, struct blob);
 	REPORT(tree, struct tree);
-	REPORT(raw_commit, struct commit);
+	REPORT(commit, struct commit);
 	REPORT(tag, struct tag);
 	REPORT(object, union any_object);
 }
diff --git a/blob.c b/blob.c
index ae320bd8fa..1fcb8e44b0 100644
--- a/blob.c
+++ b/blob.c
@@ -7,15 +7,8 @@ struct blob *lookup_blob(const unsigned char *sha1)
 {
 	struct object *obj = lookup_object(sha1);
 	if (!obj)
-		return create_object(sha1, OBJ_BLOB, alloc_blob_node());
-	if (!obj->type)
-		obj->type = OBJ_BLOB;
-	if (obj->type != OBJ_BLOB) {
-		error("Object %s is a %s, not a blob",
-		      sha1_to_hex(sha1), typename(obj->type));
-		return NULL;
-	}
-	return (struct blob *) obj;
+		return create_object(sha1, alloc_blob_node());
+	return object_as_type(obj, OBJ_BLOB, 0);
 }
 
 int parse_blob_buffer(struct blob *item, void *buffer, unsigned long size)
diff --git a/builtin/blame.c b/builtin/blame.c
index 32ce05f615..23212cbe87 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -2287,7 +2287,6 @@ static struct commit *fake_working_tree_commit(struct diff_options *opt,
 	commit = alloc_commit_node();
 	commit->object.parsed = 1;
 	commit->date = now;
-	commit->object.type = OBJ_COMMIT;
 	parent_tail = &commit->parents;
 
 	if (!resolve_ref_unsafe("HEAD", head_sha1, 1, NULL))
diff --git a/builtin/diff-tree.c b/builtin/diff-tree.c
index ce0e019e0c..1c4ad6223e 100644
--- a/builtin/diff-tree.c
+++ b/builtin/diff-tree.c
@@ -68,9 +68,7 @@ static int diff_tree_stdin(char *line)
 	line[len-1] = 0;
 	if (get_sha1_hex(line, sha1))
 		return -1;
-	obj = lookup_unknown_object(sha1);
-	if (!obj || !obj->parsed)
-		obj = parse_object(sha1);
+	obj = parse_object(sha1);
 	if (!obj)
 		return -1;
 	if (obj->type == OBJ_COMMIT)
diff --git a/cache.h b/cache.h
index 8ae30d5a85..fcb511db70 100644
--- a/cache.h
+++ b/cache.h
@@ -1402,6 +1402,7 @@ extern void *alloc_commit_node(void);
 extern void *alloc_tag_node(void);
 extern void *alloc_object_node(void);
 extern void alloc_report(void);
+extern unsigned int alloc_commit_index(void);
 
 /* pkt-line.c */
 void packet_trace_identity(const char *prog);
diff --git a/commit.c b/commit.c
index f1c9d0e2b9..90a6d2974f 100644
--- a/commit.c
+++ b/commit.c
@@ -18,19 +18,6 @@ int save_commit_buffer = 1;
 
 const char *commit_type = "commit";
 
-static struct commit *check_commit(struct object *obj,
-				   const unsigned char *sha1,
-				   int quiet)
-{
-	if (obj->type != OBJ_COMMIT) {
-		if (!quiet)
-			error("Object %s is a %s, not a commit",
-			      sha1_to_hex(sha1), typename(obj->type));
-		return NULL;
-	}
-	return (struct commit *) obj;
-}
-
 struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
 					      int quiet)
 {
@@ -38,7 +25,7 @@ struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
 
 	if (!obj)
 		return NULL;
-	return check_commit(obj, sha1, quiet);
+	return object_as_type(obj, OBJ_COMMIT, quiet);
 }
 
 struct commit *lookup_commit_reference(const unsigned char *sha1)
@@ -61,13 +48,9 @@ struct commit *lookup_commit_or_die(const unsigned char *sha1, const char *ref_n
 struct commit *lookup_commit(const unsigned char *sha1)
 {
 	struct object *obj = lookup_object(sha1);
-	if (!obj) {
-		struct commit *c = alloc_commit_node();
-		return create_object(sha1, OBJ_COMMIT, c);
-	}
-	if (!obj->type)
-		obj->type = OBJ_COMMIT;
-	return check_commit(obj, sha1, 0);
+	if (!obj)
+		return create_object(sha1, alloc_commit_node());
+	return object_as_type(obj, OBJ_COMMIT, 0);
 }
 
 struct commit *lookup_commit_reference_by_name(const char *name)
diff --git a/object.c b/object.c
index 91c7c867b9..a16b9f9e93 100644
--- a/object.c
+++ b/object.c
@@ -130,13 +130,12 @@ static void grow_object_hash(void)
 	obj_hash_size = new_hash_size;
 }
 
-void *create_object(const unsigned char *sha1, int type, void *o)
+void *create_object(const unsigned char *sha1, void *o)
 {
 	struct object *obj = o;
 
 	obj->parsed = 0;
 	obj->used = 0;
-	obj->type = type;
 	obj->flags = 0;
 	hashcpy(obj->sha1, sha1);
 
@@ -148,11 +147,30 @@ void *create_object(const unsigned char *sha1, int type, void *o)
 	return obj;
 }
 
+void *object_as_type(struct object *obj, enum object_type type, int quiet)
+{
+	if (obj->type == type)
+		return obj;
+	else if (obj->type == OBJ_NONE) {
+		if (type == OBJ_COMMIT)
+			((struct commit *)obj)->index = alloc_commit_index();
+		obj->type = type;
+		return obj;
+	}
+	else {
+		if (!quiet)
+			error("object %s is a %s, not a %s",
+			      sha1_to_hex(obj->sha1),
+			      typename(obj->type), typename(type));
+		return NULL;
+	}
+}
+
 struct object *lookup_unknown_object(const unsigned char *sha1)
 {
 	struct object *obj = lookup_object(sha1);
 	if (!obj)
-		obj = create_object(sha1, OBJ_NONE, alloc_object_node());
+		obj = create_object(sha1, alloc_object_node());
 	return obj;
 }
 
@@ -203,8 +221,6 @@ struct object *parse_object_buffer(const unsigned char *sha1, enum object_type t
 		warning("object %s has unknown type id %d", sha1_to_hex(sha1), type);
 		obj = NULL;
 	}
-	if (obj && obj->type == OBJ_NONE)
-		obj->type = type;
 	return obj;
 }
 
diff --git a/object.h b/object.h
index 6e12f2c7f4..5e8d8ee548 100644
--- a/object.h
+++ b/object.h
@@ -79,7 +79,9 @@ extern struct object *get_indexed_object(unsigned int);
  */
 struct object *lookup_object(const unsigned char *sha1);
 
-extern void *create_object(const unsigned char *sha1, int type, void *obj);
+extern void *create_object(const unsigned char *sha1, void *obj);
+
+void *object_as_type(struct object *obj, enum object_type type, int quiet);
 
 /*
  * Returns the object, having parsed it to find out what it is.
diff --git a/refs.c b/refs.c
index 3792314f3b..84b9070b8d 100644
--- a/refs.c
+++ b/refs.c
@@ -1741,9 +1741,8 @@ static enum peel_status peel_object(const unsigned char *name, unsigned char *sh
 
 	if (o->type == OBJ_NONE) {
 		int type = sha1_object_info(name, NULL);
-		if (type < 0)
+		if (type < 0 || !object_as_type(o, type, 0))
 			return PEEL_INVALID;
-		o->type = type;
 	}
 
 	if (o->type != OBJ_TAG)
diff --git a/tag.c b/tag.c
index 7b07921b30..82d841bf2d 100644
--- a/tag.c
+++ b/tag.c
@@ -40,15 +40,8 @@ struct tag *lookup_tag(const unsigned char *sha1)
 {
 	struct object *obj = lookup_object(sha1);
 	if (!obj)
-		return create_object(sha1, OBJ_TAG, alloc_tag_node());
-	if (!obj->type)
-		obj->type = OBJ_TAG;
-	if (obj->type != OBJ_TAG) {
-		error("Object %s is a %s, not a tag",
-		      sha1_to_hex(sha1), typename(obj->type));
-		return NULL;
-	}
-	return (struct tag *) obj;
+		return create_object(sha1, alloc_tag_node());
+	return object_as_type(obj, OBJ_TAG, 0);
 }
 
 static unsigned long parse_tag_date(const char *buf, const char *tail)
diff --git a/tree.c b/tree.c
index c8c49d7b78..bb02c1caa4 100644
--- a/tree.c
+++ b/tree.c
@@ -183,15 +183,8 @@ struct tree *lookup_tree(const unsigned char *sha1)
 {
 	struct object *obj = lookup_object(sha1);
 	if (!obj)
-		return create_object(sha1, OBJ_TREE, alloc_tree_node());
-	if (!obj->type)
-		obj->type = OBJ_TREE;
-	if (obj->type != OBJ_TREE) {
-		error("Object %s is a %s, not a tree",
-		      sha1_to_hex(sha1), typename(obj->type));
-		return NULL;
-	}
-	return (struct tree *) obj;
+		return create_object(sha1, alloc_tree_node());
+	return object_as_type(obj, OBJ_TREE, 0);
 }
 
 int parse_tree_buffer(struct tree *item, void *buffer, unsigned long size)