diff --git a/src/common.h b/src/common.h
index e6cf5e5..7e7801a 100644
--- a/src/common.h
+++ b/src/common.h
@@ -109,6 +109,8 @@
  */
 void *ly_realloc(void *ptr, size_t size);
 
+int lysp_check_date(struct ly_ctx *ctx, const char *date, int date_len);
+
 /*
  * Macros to work with lysp structures arrays.
  *