diff --git a/lib/genalloc.c b/lib/genalloc.c
index 2e65d20..42a95e9 100644
--- a/lib/genalloc.c
+++ b/lib/genalloc.c
@@ -415,7 +415,7 @@
 			size_t size)
 {
 	bool found = false;
-	unsigned long end = start + size;
+	unsigned long end = start + size - 1;
 	struct gen_pool_chunk *chunk;
 
 	rcu_read_lock();