Index: common/smtppass.h
--- common/smtppass.h.orig
+++ common/smtppass.h
@@ -71,7 +71,7 @@ typedef struct spio
     char localname[MAXPATHLEN];         /* Address where we accepted the connection */
     
     /* Internal use only */
-    char line[SP_LINE_LENGTH];  
+    char line[SP_LINE_LENGTH + 1];	/* space for trailing nul */
     char* _nx;
     size_t _ln;                         
 }
