diff --git a/src/tt.h b/src/tt.h
index dd667841..a983805b 100644
--- a/src/tt.h
+++ b/src/tt.h
@@ -50,7 +50,7 @@ struct TTEntry {
     // Don't overwrite more valuable entries
     if (  (k >> 48) != key16
         || d > depth8 - 2
-     /* || g != (genBound8 & 0xFC) // Any matching keys are already refreshed by probe() */
+     /* || g != (genBound8 & 0xFC) // Matching non-zero keys are already refreshed by probe() */
         || b == BOUND_EXACT)
     {
         key16     = (uint16_t)(k >> 48);