diff --git a/src/ucl_parser.c b/src/ucl_parser.c
index d6ea46e..b7c8b9f 100644
--- a/src/ucl_parser.c
+++ b/src/ucl_parser.c
@@ -567,15 +567,13 @@ ucl_parse_key (struct ucl_parser *parser,
 		else {
 			/* Parse the body of a key */
 			if (!got_quote) {
-				if (isalnum (*p)) {
-					ucl_chunk_skipc (chunk, *p);
-					p ++;
-				}
-				else if (*p == ' ' || *p == '\t' || *p == ':' || *p == '=') {
+				if (*p == ' ' || *p == '\t' || *p == ':' || *p == '=') {
 					end = p;
 					break;
-				}
-				else {
+				} else if (iswprint (*p)) {
+					ucl_chunk_skipc (chunk, *p);
+					p ++;
+				} else {
 					ucl_set_err (chunk, UCL_ESYNTAX, "invalid character in a key", err);
 					return false;
 				}