diff --git a/include/spdk/nvme_spec.h b/include/spdk/nvme_spec.h
index 8c53e4fa8..bc645345c 100644
--- a/include/spdk/nvme_spec.h
+++ b/include/spdk/nvme_spec.h
@@ -845,6 +845,10 @@ enum spdk_nvmf_ctrlr_model {
 	SPDK_NVMF_CTRLR_MODEL_STATIC			= 1,
 };
 
+#define SPDK_NVME_CTRLR_SN_LEN	20
+#define SPDK_NVME_CTRLR_MN_LEN	40
+#define SPDK_NVME_CTRLR_FR_LEN	8
+
 struct __attribute__((packed)) spdk_nvme_ctrlr_data {
 	/* bytes 0-255: controller capabilities and features */
 
@@ -855,13 +859,13 @@ struct __attribute__((packed)) spdk_nvme_ctrlr_data {
 	uint16_t		ssvid;
 
 	/** serial number */
-	int8_t			sn[20];
+	int8_t			sn[SPDK_NVME_CTRLR_SN_LEN];
 
 	/** model number */
-	int8_t			mn[40];
+	int8_t			mn[SPDK_NVME_CTRLR_MN_LEN];
 
 	/** firmware revision */
-	uint8_t			fr[8];
+	uint8_t			fr[SPDK_NVME_CTRLR_FR_LEN];
 
 	/** recommended arbitration burst */
 	uint8_t			rab;
diff --git a/include/spdk/nvmf.h b/include/spdk/nvmf.h
index 4e81f3b92..de75ea92b 100644
--- a/include/spdk/nvmf.h
+++ b/include/spdk/nvmf.h
@@ -46,7 +46,6 @@
 #include "spdk/queue.h"
 
 #define MAX_VIRTUAL_NAMESPACE 16
-#define MAX_SN_LEN 20
 
 struct spdk_nvmf_tgt;
 
diff --git a/lib/nvmf/nvmf_internal.h b/lib/nvmf/nvmf_internal.h
index 76e81e572..c95f2a449 100644
--- a/lib/nvmf/nvmf_internal.h
+++ b/lib/nvmf/nvmf_internal.h
@@ -88,7 +88,7 @@ struct spdk_nvmf_subsystem {
 
 	struct spdk_nvmf_tgt			*tgt;
 
-	char sn[MAX_SN_LEN + 1];
+	char sn[SPDK_NVME_CTRLR_SN_LEN + 1];
 
 	struct spdk_nvmf_ns			ns[MAX_VIRTUAL_NAMESPACE];
 	uint32_t 				max_nsid;