diff --git a/lib/reduce/reduce.c b/lib/reduce/reduce.c
index 123b115e4..fd5e6f0d4 100644
--- a/lib/reduce/reduce.c
+++ b/lib/reduce/reduce.c
@@ -45,8 +45,6 @@
 /* Always round up the size of the PM region to the nearest cacheline. */
 #define REDUCE_PM_SIZE_ALIGNMENT	64
 
-#define SPDK_REDUCE_SIGNATURE "SPDKREDU"
-
 /* Offset into the backing device where the persistent memory file's path is stored. */
 #define REDUCE_BACKING_DEV_PATH_OFFSET	4096
 
@@ -62,6 +60,11 @@ struct spdk_reduce_vol_superblock {
 };
 SPDK_STATIC_ASSERT(sizeof(struct spdk_reduce_vol_superblock) == 4096, "size incorrect");
 
+#define SPDK_REDUCE_SIGNATURE "SPDKREDU"
+/* null terminator counts one */
+SPDK_STATIC_ASSERT(sizeof(SPDK_REDUCE_SIGNATURE) - 1 ==
+		   sizeof(((struct spdk_reduce_vol_superblock *)0)->signature), "size incorrect");
+
 #define REDUCE_PATH_MAX 4096
 
 /**