diff --git a/src/fileio.c b/src/fileio.c
index b099461..967f49e 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -4817,11 +4817,8 @@
 	    STRCAT(IObuff, _(" CONVERSION ERROR"));
 	    c = TRUE;
 	    if (write_info.bw_conv_error_lnum != 0)
-	    {
-		size_t l = STRLEN(IObuff);
-		vim_snprintf((char *)IObuff + l, IOSIZE - l, _(" in line %ld;"),
+		vim_snprintf_add((char *)IObuff, IOSIZE, _(" in line %ld;"),
 			(long)write_info.bw_conv_error_lnum);
-	    }
 	}
 	else if (notconverted)
 	{