diff --git a/src/in_internal.h b/src/in_internal.h
index 684487f..11f33c3 100644
--- a/src/in_internal.h
+++ b/src/in_internal.h
@@ -35,9 +35,17 @@
             char *filepath; /**< stored original filepath */
         } fpath;            /**< filepath structure for LY_IN_FILEPATH */
     } method;               /**< type-specific information about the output */
+    uint64_t line;          /**< current line of the input */
 };
 
 /**
+ * @brief Increment line counter.
+ * @param[in] IN The input handler.
+ */
+#define LY_IN_NEW_LINE(IN) \
+    (IN)->line++
+
+/**
  * @brief Read bytes from an input.
  *
  * @param[in] in Input structure.