diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 874faa6b..67e05921 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -768,7 +768,7 @@ namespace {
         {
             if (   pos.non_pawn_material(WHITE) == BishopValueMg
                 && pos.non_pawn_material(BLACK) == BishopValueMg)
-                sf = 22;
+                sf = 18 + 4 * popcount(pe->passed_pawns(strongSide));
             else
                 sf = 22 + 3 * pos.count<ALL_PIECES>(strongSide);
         }