diff --git a/reftable/basics.c b/reftable/basics.c
index 70b1091d14..fe2b83ff83 100644
--- a/reftable/basics.c
+++ b/reftable/basics.c
@@ -124,11 +124,8 @@ int reftable_buf_add(struct reftable_buf *buf, const void *data, size_t len)
 	size_t newlen = buf->len + len;
 
 	if (newlen + 1 > buf->alloc) {
-		char *reallocated = buf->buf;
-		REFTABLE_ALLOC_GROW(reallocated, newlen + 1, buf->alloc);
-		if (!reallocated)
+		if (REFTABLE_ALLOC_GROW(buf->buf, newlen + 1, buf->alloc))
 			return REFTABLE_OUT_OF_MEMORY_ERROR;
-		buf->buf = reallocated;
 	}
 
 	memcpy(buf->buf + buf->len, data, len);
@@ -233,11 +230,9 @@ char **parse_names(char *buf, int size)
 			next = end;
 		}
 		if (p < next) {
-			char **names_grown = names;
-			REFTABLE_ALLOC_GROW(names_grown, names_len + 1, names_cap);
-			if (!names_grown)
+			if (REFTABLE_ALLOC_GROW(names, names_len + 1,
+						names_cap))
 				goto err;
-			names = names_grown;
 
 			names[names_len] = reftable_strdup(p);
 			if (!names[names_len++])
@@ -246,7 +241,8 @@ char **parse_names(char *buf, int size)
 		p = next + 1;
 	}
 
-	REFTABLE_REALLOC_ARRAY(names, names_len + 1);
+	if (REFTABLE_ALLOC_GROW(names, names_len + 1, names_cap))
+		goto err;
 	names[names_len] = NULL;
 
 	return names;
diff --git a/reftable/basics.h b/reftable/basics.h
index 36beda2c25..4bf71b0954 100644
--- a/reftable/basics.h
+++ b/reftable/basics.h
@@ -120,15 +120,38 @@ char *reftable_strdup(const char *str);
 #define REFTABLE_ALLOC_ARRAY(x, alloc) (x) = reftable_malloc(st_mult(sizeof(*(x)), (alloc)))
 #define REFTABLE_CALLOC_ARRAY(x, alloc) (x) = reftable_calloc((alloc), sizeof(*(x)))
 #define REFTABLE_REALLOC_ARRAY(x, alloc) (x) = reftable_realloc((x), st_mult(sizeof(*(x)), (alloc)))
-#define REFTABLE_ALLOC_GROW(x, nr, alloc) \
-	do { \
-		if ((nr) > alloc) { \
-			alloc = 2 * (alloc) + 1; \
-			if (alloc < (nr)) \
-				alloc = (nr); \
-			REFTABLE_REALLOC_ARRAY(x, alloc); \
-		} \
-	} while (0)
+
+static inline void *reftable_alloc_grow(void *p, size_t nelem, size_t elsize,
+					size_t *allocp)
+{
+	void *new_p;
+	size_t alloc = *allocp * 2 + 1;
+	if (alloc < nelem)
+		alloc = nelem;
+	new_p = reftable_realloc(p, st_mult(elsize, alloc));
+	if (!new_p)
+		return p;
+	*allocp = alloc;
+	return new_p;
+}
+
+#define REFTABLE_ALLOC_GROW(x, nr, alloc) ( \
+	(nr) > (alloc) && ( \
+		(x) = reftable_alloc_grow((x), (nr), sizeof(*(x)), &(alloc)), \
+		(nr) > (alloc) \
+	) \
+)
+
+#define REFTABLE_ALLOC_GROW_OR_NULL(x, nr, alloc) do { \
+	size_t reftable_alloc_grow_or_null_alloc = alloc; \
+	if (REFTABLE_ALLOC_GROW((x), (nr), reftable_alloc_grow_or_null_alloc)) { \
+		REFTABLE_FREE_AND_NULL(x); \
+		alloc = 0; \
+	} else { \
+		alloc = reftable_alloc_grow_or_null_alloc; \
+	} \
+} while (0)
+
 #define REFTABLE_FREE_AND_NULL(p) do { reftable_free(p); (p) = NULL; } while (0)
 
 #ifndef REFTABLE_ALLOW_BANNED_ALLOCATORS
diff --git a/reftable/block.c b/reftable/block.c
index 0198078485..9858bbc7c5 100644
--- a/reftable/block.c
+++ b/reftable/block.c
@@ -53,7 +53,8 @@ static int block_writer_register_restart(struct block_writer *w, int n,
 	if (2 + 3 * rlen + n > w->block_size - w->next)
 		return -1;
 	if (is_restart) {
-		REFTABLE_ALLOC_GROW(w->restarts, w->restart_len + 1, w->restart_cap);
+		REFTABLE_ALLOC_GROW_OR_NULL(w->restarts, w->restart_len + 1,
+					    w->restart_cap);
 		if (!w->restarts)
 			return REFTABLE_OUT_OF_MEMORY_ERROR;
 		w->restarts[w->restart_len++] = w->next;
@@ -176,7 +177,8 @@ int block_writer_finish(struct block_writer *w)
 		 * is guaranteed to return `Z_STREAM_END`.
 		 */
 		compressed_len = deflateBound(w->zstream, src_len);
-		REFTABLE_ALLOC_GROW(w->compressed, compressed_len, w->compressed_cap);
+		REFTABLE_ALLOC_GROW_OR_NULL(w->compressed, compressed_len,
+					    w->compressed_cap);
 		if (!w->compressed) {
 			ret = REFTABLE_OUT_OF_MEMORY_ERROR;
 			return ret;
@@ -235,8 +237,8 @@ int block_reader_init(struct block_reader *br, struct reftable_block *block,
 		uLong src_len = block->len - block_header_skip;
 
 		/* Log blocks specify the *uncompressed* size in their header. */
-		REFTABLE_ALLOC_GROW(br->uncompressed_data, sz,
-				    br->uncompressed_cap);
+		REFTABLE_ALLOC_GROW_OR_NULL(br->uncompressed_data, sz,
+					    br->uncompressed_cap);
 		if (!br->uncompressed_data) {
 			err = REFTABLE_OUT_OF_MEMORY_ERROR;
 			goto done;
diff --git a/reftable/pq.c b/reftable/pq.c
index 6ee1164dd3..5591e875e1 100644
--- a/reftable/pq.c
+++ b/reftable/pq.c
@@ -49,7 +49,7 @@ int merged_iter_pqueue_add(struct merged_iter_pqueue *pq, const struct pq_entry
 {
 	size_t i = 0;
 
-	REFTABLE_ALLOC_GROW(pq->heap, pq->len + 1, pq->cap);
+	REFTABLE_ALLOC_GROW_OR_NULL(pq->heap, pq->len + 1, pq->cap);
 	if (!pq->heap)
 		return REFTABLE_OUT_OF_MEMORY_ERROR;
 	pq->heap[pq->len++] = *e;
diff --git a/reftable/record.c b/reftable/record.c
index fb5652ed57..04429d23fe 100644
--- a/reftable/record.c
+++ b/reftable/record.c
@@ -246,8 +246,8 @@ static int reftable_ref_record_copy_from(void *rec, const void *src_rec,
 	if (src->refname) {
 		size_t refname_len = strlen(src->refname);
 
-		REFTABLE_ALLOC_GROW(ref->refname, refname_len + 1,
-				    ref->refname_cap);
+		REFTABLE_ALLOC_GROW_OR_NULL(ref->refname, refname_len + 1,
+					    ref->refname_cap);
 		if (!ref->refname) {
 			err = REFTABLE_OUT_OF_MEMORY_ERROR;
 			goto out;
@@ -385,7 +385,7 @@ static int reftable_ref_record_decode(void *rec, struct reftable_buf key,
 	SWAP(r->refname, refname);
 	SWAP(r->refname_cap, refname_cap);
 
-	REFTABLE_ALLOC_GROW(r->refname, key.len + 1, r->refname_cap);
+	REFTABLE_ALLOC_GROW_OR_NULL(r->refname, key.len + 1, r->refname_cap);
 	if (!r->refname) {
 		err = REFTABLE_OUT_OF_MEMORY_ERROR;
 		goto done;
@@ -839,7 +839,7 @@ static int reftable_log_record_decode(void *rec, struct reftable_buf key,
 	if (key.len <= 9 || key.buf[key.len - 9] != 0)
 		return REFTABLE_FORMAT_ERROR;
 
-	REFTABLE_ALLOC_GROW(r->refname, key.len - 8, r->refname_cap);
+	REFTABLE_ALLOC_GROW_OR_NULL(r->refname, key.len - 8, r->refname_cap);
 	if (!r->refname) {
 		err = REFTABLE_OUT_OF_MEMORY_ERROR;
 		goto done;
@@ -947,8 +947,8 @@ static int reftable_log_record_decode(void *rec, struct reftable_buf key,
 	}
 	string_view_consume(&in, n);
 
-	REFTABLE_ALLOC_GROW(r->value.update.message, scratch->len + 1,
-			    r->value.update.message_cap);
+	REFTABLE_ALLOC_GROW_OR_NULL(r->value.update.message, scratch->len + 1,
+				    r->value.update.message_cap);
 	if (!r->value.update.message) {
 		err = REFTABLE_OUT_OF_MEMORY_ERROR;
 		goto done;
diff --git a/reftable/stack.c b/reftable/stack.c
index 634f0c5425..531660a49f 100644
--- a/reftable/stack.c
+++ b/reftable/stack.c
@@ -317,7 +317,9 @@ static int reftable_stack_reload_once(struct reftable_stack *st,
 				 * thus need to keep them alive here, which we
 				 * do by bumping their refcount.
 				 */
-				REFTABLE_ALLOC_GROW(reused, reused_len + 1, reused_alloc);
+				REFTABLE_ALLOC_GROW_OR_NULL(reused,
+							    reused_len + 1,
+							    reused_alloc);
 				if (!reused) {
 					err = REFTABLE_OUT_OF_MEMORY_ERROR;
 					goto done;
@@ -949,8 +951,8 @@ int reftable_addition_add(struct reftable_addition *add,
 	if (err < 0)
 		goto done;
 
-	REFTABLE_ALLOC_GROW(add->new_tables, add->new_tables_len + 1,
-			    add->new_tables_cap);
+	REFTABLE_ALLOC_GROW_OR_NULL(add->new_tables, add->new_tables_len + 1,
+				    add->new_tables_cap);
 	if (!add->new_tables) {
 		err = REFTABLE_OUT_OF_MEMORY_ERROR;
 		goto done;
diff --git a/reftable/writer.c b/reftable/writer.c
index 624e90fb53..740c98038e 100644
--- a/reftable/writer.c
+++ b/reftable/writer.c
@@ -254,7 +254,8 @@ static int writer_index_hash(struct reftable_writer *w, struct reftable_buf *has
 	if (key->offset_len > 0 && key->offsets[key->offset_len - 1] == off)
 		return 0;
 
-	REFTABLE_ALLOC_GROW(key->offsets, key->offset_len + 1, key->offset_cap);
+	REFTABLE_ALLOC_GROW_OR_NULL(key->offsets, key->offset_len + 1,
+				    key->offset_cap);
 	if (!key->offsets)
 		return REFTABLE_OUT_OF_MEMORY_ERROR;
 	key->offsets[key->offset_len++] = off;
@@ -820,7 +821,7 @@ static int writer_flush_nonempty_block(struct reftable_writer *w)
 	 * Note that this also applies when flushing index blocks, in which
 	 * case we will end up with a multi-level index.
 	 */
-	REFTABLE_ALLOC_GROW(w->index, w->index_len + 1, w->index_cap);
+	REFTABLE_ALLOC_GROW_OR_NULL(w->index, w->index_len + 1, w->index_cap);
 	if (!w->index)
 		return REFTABLE_OUT_OF_MEMORY_ERROR;
 
diff --git a/t/unit-tests/t-reftable-basics.c b/t/unit-tests/t-reftable-basics.c
index 65d50df091..990dc1a244 100644
--- a/t/unit-tests/t-reftable-basics.c
+++ b/t/unit-tests/t-reftable-basics.c
@@ -20,6 +20,11 @@ static int integer_needle_lesseq(size_t i, void *_args)
 	return args->needle <= args->haystack[i];
 }
 
+static void *realloc_stub(void *p UNUSED, size_t size UNUSED)
+{
+	return NULL;
+}
+
 int cmd_main(int argc UNUSED, const char *argv[] UNUSED)
 {
 	if_test ("binary search with binsearch works") {
@@ -141,5 +146,56 @@ int cmd_main(int argc UNUSED, const char *argv[] UNUSED)
 		check_int(in, ==, out);
 	}
 
+	if_test ("REFTABLE_ALLOC_GROW works") {
+		int *arr = NULL, *old_arr;
+		size_t alloc = 0, old_alloc;
+
+		check(!REFTABLE_ALLOC_GROW(arr, 1, alloc));
+		check(arr != NULL);
+		check_uint(alloc, >=, 1);
+		arr[0] = 42;
+
+		old_alloc = alloc;
+		old_arr = arr;
+		reftable_set_alloc(malloc, realloc_stub, free);
+		check(REFTABLE_ALLOC_GROW(arr, old_alloc + 1, alloc));
+		check(arr == old_arr);
+		check_uint(alloc, ==, old_alloc);
+
+		old_alloc = alloc;
+		reftable_set_alloc(malloc, realloc, free);
+		check(!REFTABLE_ALLOC_GROW(arr, old_alloc + 1, alloc));
+		check(arr != NULL);
+		check_uint(alloc, >, old_alloc);
+		arr[alloc - 1] = 42;
+
+		reftable_free(arr);
+	}
+
+	if_test ("REFTABLE_ALLOC_GROW_OR_NULL works") {
+		int *arr = NULL;
+		size_t alloc = 0, old_alloc;
+
+		REFTABLE_ALLOC_GROW_OR_NULL(arr, 1, alloc);
+		check(arr != NULL);
+		check_uint(alloc, >=, 1);
+		arr[0] = 42;
+
+		old_alloc = alloc;
+		REFTABLE_ALLOC_GROW_OR_NULL(arr, old_alloc + 1, alloc);
+		check(arr != NULL);
+		check_uint(alloc, >, old_alloc);
+		arr[alloc - 1] = 42;
+
+		old_alloc = alloc;
+		reftable_set_alloc(malloc, realloc_stub, free);
+		REFTABLE_ALLOC_GROW_OR_NULL(arr, old_alloc + 1, alloc);
+		check(arr == NULL);
+		check_uint(alloc, ==, 0);
+		reftable_set_alloc(malloc, realloc, free);
+
+		reftable_free(arr);
+	}
+
 	return test_done();
 }
diff --git a/t/unit-tests/t-reftable-merged.c b/t/unit-tests/t-reftable-merged.c
index a12bd0e1a3..60836f80d6 100644
--- a/t/unit-tests/t-reftable-merged.c
+++ b/t/unit-tests/t-reftable-merged.c
@@ -178,7 +178,7 @@ static void t_merged_refs(void)
 		if (err > 0)
 			break;
 
-		REFTABLE_ALLOC_GROW(out, len + 1, cap);
+		check(!REFTABLE_ALLOC_GROW(out, len + 1, cap));
 		out[len++] = ref;
 	}
 	reftable_iterator_destroy(&it);
@@ -459,7 +459,7 @@ static void t_merged_logs(void)
 		if (err > 0)
 			break;
 
-		REFTABLE_ALLOC_GROW(out, len + 1, cap);
+		check(!REFTABLE_ALLOC_GROW(out, len + 1, cap));
 		out[len++] = log;
 	}
 	reftable_iterator_destroy(&it);