diff --git a/src/option.c b/src/option.c
index a4a9c97..e6d46aa 100644
--- a/src/option.c
+++ b/src/option.c
@@ -7758,10 +7758,13 @@
 	     * '.encoding'.
 	     */
 	    for (p = q; *p != NUL; ++p)
-		if (vim_strchr((char_u *)"_.,", *p) != NULL)
+		if (!ASCII_ISALPHA(*p) && *p != '-')
 		    break;
-	    vim_snprintf((char *)fname, 200, "spell/%.*s.vim", (int)(p - q), q);
-	    source_runtime(fname, DIP_ALL);
+	    if (p > q)
+	    {
+		vim_snprintf((char *)fname, 200, "spell/%.*s.vim", (int)(p - q), q);
+		source_runtime(fname, DIP_ALL);
+	    }
 	}
 #endif
     }