diff --git a/mem-pool.c b/mem-pool.c
index 020b51e0c5..7659919ab2 100644
--- a/mem-pool.c
+++ b/mem-pool.c
@@ -33,21 +33,13 @@ static struct mp_block *mem_pool_alloc_block(struct mem_pool *mem_pool, size_t b
 	return p;
 }
 
-void mem_pool_init(struct mem_pool **mem_pool, size_t initial_size)
+void mem_pool_init(struct mem_pool *pool, size_t initial_size)
 {
-	struct mem_pool *pool;
-
-	if (*mem_pool)
-		return;
-
-	pool = xcalloc(1, sizeof(*pool));
-
+	memset(pool, 0, sizeof(*pool));
 	pool->block_alloc = BLOCK_GROWTH_SIZE;
 
 	if (initial_size > 0)
 		mem_pool_alloc_block(pool, initial_size, NULL);
-
-	*mem_pool = pool;
 }
 
 void mem_pool_discard(struct mem_pool *mem_pool, int invalidate_memory)
@@ -66,7 +58,8 @@ void mem_pool_discard(struct mem_pool *mem_pool, int invalidate_memory)
 		free(block_to_free);
 	}
 
-	free(mem_pool);
+	mem_pool->mp_block = NULL;
+	mem_pool->pool_alloc = 0;
 }
 
 void *mem_pool_alloc(struct mem_pool *mem_pool, size_t len)
diff --git a/mem-pool.h b/mem-pool.h
index ca062c9070..870161ab44 100644
--- a/mem-pool.h
+++ b/mem-pool.h
@@ -24,10 +24,10 @@ struct mem_pool {
 /*
  * Initialize mem_pool with specified initial size.
  */
-void mem_pool_init(struct mem_pool **mem_pool, size_t initial_size);
+void mem_pool_init(struct mem_pool *pool, size_t initial_size);
 
 /*
- * Discard a memory pool and free all the memory it is responsible for.
+ * Discard all the memory the memory pool is responsible for.
  */
 void mem_pool_discard(struct mem_pool *mem_pool, int invalidate_memory);
 
diff --git a/read-cache.c b/read-cache.c
index 8ed1c29b54..fa291cdbee 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -89,8 +89,10 @@ static struct mem_pool *find_mem_pool(struct index_state *istate)
 	else
 		pool_ptr = &istate->ce_mem_pool;
 
-	if (!*pool_ptr)
-		mem_pool_init(pool_ptr, 0);
+	if (!*pool_ptr) {
+		*pool_ptr = xmalloc(sizeof(**pool_ptr));
+		mem_pool_init(*pool_ptr, 0);
+	}
 
 	return *pool_ptr;
 }
@@ -2006,11 +2008,12 @@ static unsigned long load_all_cache_entries(struct index_state *istate,
 {
 	unsigned long consumed;
 
+	istate->ce_mem_pool = xmalloc(sizeof(*istate->ce_mem_pool));
 	if (istate->version == 4) {
-		mem_pool_init(&istate->ce_mem_pool,
+		mem_pool_init(istate->ce_mem_pool,
 				estimate_cache_size_from_compressed(istate->cache_nr));
 	} else {
-		mem_pool_init(&istate->ce_mem_pool,
+		mem_pool_init(istate->ce_mem_pool,
 				estimate_cache_size(mmap_size, istate->cache_nr));
 	}
 
@@ -2070,7 +2073,8 @@ static unsigned long load_cache_entries_threaded(struct index_state *istate, con
 	if (istate->name_hash_initialized)
 		BUG("the name hash isn't thread safe");
 
-	mem_pool_init(&istate->ce_mem_pool, 0);
+	istate->ce_mem_pool = xmalloc(sizeof(*istate->ce_mem_pool));
+	mem_pool_init(istate->ce_mem_pool, 0);
 
 	/* ensure we have no more threads than we have blocks to process */
 	if (nr_threads > ieot->nr)
@@ -2097,11 +2101,12 @@ static unsigned long load_cache_entries_threaded(struct index_state *istate, con
 		nr = 0;
 		for (j = p->ieot_start; j < p->ieot_start + p->ieot_blocks; j++)
 			nr += p->ieot->entries[j].nr;
+		istate->ce_mem_pool = xmalloc(sizeof(*istate->ce_mem_pool));
 		if (istate->version == 4) {
-			mem_pool_init(&p->ce_mem_pool,
+			mem_pool_init(p->ce_mem_pool,
 				estimate_cache_size_from_compressed(nr));
 		} else {
-			mem_pool_init(&p->ce_mem_pool,
+			mem_pool_init(p->ce_mem_pool,
 				estimate_cache_size(mmap_size, nr));
 		}
 
@@ -2358,7 +2363,7 @@ int discard_index(struct index_state *istate)
 
 	if (istate->ce_mem_pool) {
 		mem_pool_discard(istate->ce_mem_pool, should_validate_cache_entries());
-		istate->ce_mem_pool = NULL;
+		FREE_AND_NULL(istate->ce_mem_pool);
 	}
 
 	return 0;
diff --git a/split-index.c b/split-index.c
index e6154e4ea9..c0e8ad670d 100644
--- a/split-index.c
+++ b/split-index.c
@@ -79,8 +79,10 @@ void move_cache_to_base_index(struct index_state *istate)
 	if (si->base &&
 		si->base->ce_mem_pool) {
 
-		if (!istate->ce_mem_pool)
-			mem_pool_init(&istate->ce_mem_pool, 0);
+		if (!istate->ce_mem_pool) {
+			istate->ce_mem_pool = xmalloc(sizeof(struct mem_pool));
+			mem_pool_init(istate->ce_mem_pool, 0);
+		}
 
 		mem_pool_combine(istate->ce_mem_pool, istate->split_index->base->ce_mem_pool);
 	}