diff --git a/drivers/s390/scsi/zfcp_def.h b/drivers/s390/scsi/zfcp_def.h
index 87a1fef5568e..13bfc13eb42d 100644
--- a/drivers/s390/scsi/zfcp_def.h
+++ b/drivers/s390/scsi/zfcp_def.h
@@ -49,8 +49,8 @@
 /*************** ADAPTER/PORT/UNIT AND FSF_REQ STATUS FLAGS ******************/
 
 /*
- * Note, the leftmost status byte is common among adapter, port
- * and unit
+ * Note, the leftmost 12 status bits (3 nibbles) are common among adapter, port
+ * and unit. This is a mask for bitwise 'and' with status values.
  */
 #define ZFCP_COMMON_FLAGS			0xfff00000