diff --git a/src/regex/regcomp.c b/src/regex/regcomp.c
index 978dd87..d7e7a9c 100644
--- a/src/regex/regcomp.c
+++ b/src/regex/regcomp.c
@@ -1008,13 +1008,18 @@ static reg_errcode_t tre_parse(tre_parse_ctx_t *ctx)
 		nbranch = tre_ast_new_catenation(ctx->mem, nbranch, ctx->n);
 		if ((ere && *s == '|') ||
 		    (ere && *s == ')' && depth) ||
-		    (!ere && *s == '\\' && s[1] == ')') ||
+		    (!ere && *s == '\\' && (s[1] == ')' || s[1] == '|')) ||
 		    !*s) {
 			/* extension: empty branch is unspecified (), (|a), (a|)
 			   here they are not rejected but match on empty string */
 			int c = *s;
 			nunion = tre_ast_new_union(ctx->mem, nunion, nbranch);
 			nbranch = 0;
+
+			if (c == '\\' && s[1] == '|') {
+				s++;
+				c = '|';
+			}
 			if (c != '|') {
 				if (c == '\\') {
 					if (!depth) return REG_EPAREN;