diff --git a/core/src/ser.rs b/core/src/ser.rs
index b18910bdd..cbbb1ec3b 100644
--- a/core/src/ser.rs
+++ b/core/src/ser.rs
@@ -565,14 +565,14 @@ pub trait PMMRIndexHashable {
 
 impl<T: PMMRable> PMMRIndexHashable for T {
 	fn hash_with_index(&self, index: u64) -> Hash {
-		(self, index).hash()
+		(index, self).hash()
 	}
 }
 
 // Convenient way to hash two existing hashes together with an index.
 impl PMMRIndexHashable for (Hash, Hash) {
 	fn hash_with_index(&self, index: u64) -> Hash {
-		(&self.0, &self.1, index).hash()
+		(index, &self.0, &self.1).hash()
 	}
 }