diff --git a/client/db/src/kv/mod.rs b/client/db/src/kv/mod.rs
index 74d3c10ed3..03b00f01c0 100644
--- a/client/db/src/kv/mod.rs
+++ b/client/db/src/kv/mod.rs
@@ -308,13 +308,15 @@ impl<Block: BlockT> MappingDb<Block> {
 
 		let substrate_hashes = match self.block_hash(&commitment.ethereum_block_hash) {
 			Ok(Some(mut data)) => {
-				data.push(commitment.block_hash);
-				log::warn!(
-					target: "fc-db",
-					"Possible equivocation at ethereum block hash {} {:?}",
-					&commitment.ethereum_block_hash,
-					&data
-				);
+				if !data.contains(&commitment.block_hash) {
+					data.push(commitment.block_hash);
+					log::warn!(
+						target: "fc-db",
+						"Possible equivocation at ethereum block hash {} {:?}",
+						&commitment.ethereum_block_hash,
+						&data
+					);
+				}
 				data
 			}
 			_ => vec![commitment.block_hash],