diff --git a/src/regex/regcomp.c b/src/regex/regcomp.c
index ea6e6a6942ab7a7d9af5871153b1f8003233cfe6..712ca80db976ed6c9332d205e623d8c6ac68b6a6 100644
--- a/src/regex/regcomp.c
+++ b/src/regex/regcomp.c
@@ -1353,6 +1353,8 @@ tre_parse(tre_parse_ctx_t *ctx)
 	      if (ctx->cflags & REG_EXTENDED
 		  || ctx->re == ctx->re_start)
 		{
+		  if (!(ctx->cflags & REG_EXTENDED))
+		    STACK_PUSHX(stack, int, PARSE_CATENATION);
 		  result = tre_ast_new_literal(ctx->mem, ASSERTION,
 					       ASSERT_AT_BOL, -1);
 		  if (result == NULL)