diff --git a/src/os_unix.c b/src/os_unix.c
index bd7b219..0e27609 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -8032,7 +8032,7 @@
 	    &smcallbacks,
 	    NULL,
 	    &xsmp.clientid,
-	    sizeof(errorstring),
+	    sizeof(errorstring) - 1,
 	    errorstring);
     if (xsmp.smcconn == NULL)
     {