diff --git a/src/validation.h b/src/validation.h
index 4ecefb5..704d4b3 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -17,6 +17,7 @@
 
 #include <stdint.h>
 
+#include "diff.h"
 #include "log.h"
 
 struct ly_ctx;
@@ -25,8 +26,6 @@
 struct lys_module;
 struct lysc_node;
 
-enum lyd_diff_op;
-
 /**
  * @brief Add information about the node's extensions having their own validation callback into an unres set.
  *