diff --git a/vlib/hash/hash.v b/vlib/hash/hash.v
index 2c610133b9b2f8..4fbd37fd6df30f 100644
--- a/vlib/hash/hash.v
+++ b/vlib/hash/hash.v
@@ -4,11 +4,15 @@
 module hash
 
 pub interface Hash {
+mut:
 	// Sum appends the current hash to b and returns the resulting array.
 	// It does not change the underlying hash state.
 	sum(b []u8) []u8
 	size() int
 	block_size() int
+	free()
+	reset()
+	write(p []u8) !int
 }
 
 interface Hash32er {