diff --git a/src/search/transposition_table.rs b/src/search/transposition_table.rs
index dec0f20..06642c9 100644
--- a/src/search/transposition_table.rs
+++ b/src/search/transposition_table.rs
@@ -25,12 +25,12 @@ impl TranspositionTable {
 
     pub fn lookup(&self, zobrist_hash: ZobristHash) -> Option<TTEntry> {
         self.positions
-            .get((zobrist_hash.0 % self.size) as usize)
+            .get((zobrist_hash.0 & (self.size - 1)) as usize)
             .and_then(|entry| *entry)
     }
 
     pub fn insert(&mut self, entry: TTEntry) {
-        let idx = (entry.hash.0 % self.size) as usize;
+        let idx = (entry.hash.0 & (self.size - 1)) as usize;
         self.positions[idx] = Some(entry);
     }
 }