diff --git a/xwords4/common/comtypes.h b/xwords4/common/comtypes.h
index d2c35f93b..2779b4906 100644
--- a/xwords4/common/comtypes.h
+++ b/xwords4/common/comtypes.h
@@ -212,6 +212,8 @@ typedef enum {
     BONUS_DOUBLE_WORD,
     BONUS_TRIPLE_LETTER,
     BONUS_TRIPLE_WORD,
+    BONUS_QUAD_LETTER,
+    BONUS_QUAD_WORD,
 
     BONUS_LAST
 } XWBonusType;
diff --git a/xwords4/common/model.c b/xwords4/common/model.c
index 016355898..1381142da 100644
--- a/xwords4/common/model.c
+++ b/xwords4/common/model.c
@@ -391,7 +391,7 @@ model_setSquareBonuses( ModelCtxt* model, XWBonusType* bonuses, XP_U16 nBonuses
         XP_FREE( model->vol.mpool, model->vol.bonuses );
     }
     model->vol.bonuses = XP_MALLOC( model->vol.mpool, 
-                                nBonuses * sizeof(model->vol.bonuses[0]) );
+                                    nBonuses * sizeof(model->vol.bonuses[0]) );
     XP_MEMCPY( model->vol.bonuses, bonuses, 
                nBonuses * sizeof(model->vol.bonuses[0]) );
     model->vol.nBonuses = nBonuses;
diff --git a/xwords4/common/mscore.c b/xwords4/common/mscore.c
index 2fbc18cf3..cdc54abc8 100644
--- a/xwords4/common/mscore.c
+++ b/xwords4/common/mscore.c
@@ -620,6 +620,8 @@ word_multiplier( const ModelCtxt* model, XWEnv xwe, XP_U16 col, XP_U16 row )
         return 2;
     case BONUS_TRIPLE_WORD:
         return 3;
+    case BONUS_QUAD_WORD:
+        return 4;
     default:
         return 1;
     }
@@ -634,6 +636,8 @@ tile_multiplier( const ModelCtxt* model, XWEnv xwe, XP_U16 col, XP_U16 row )
         return 2;
     case BONUS_TRIPLE_LETTER:
         return 3;
+    case BONUS_QUAD_LETTER:
+        return 4;
     default:
         return 1;
     }
diff --git a/xwords4/linux/linuxutl.c b/xwords4/linux/linuxutl.c
index 3f52ad43a..6101b820d 100644
--- a/xwords4/linux/linuxutl.c
+++ b/xwords4/linux/linuxutl.c
@@ -115,11 +115,13 @@ linux_util_makeEmptyDict( XW_UtilCtxt* XP_UNUSED_DBG(uctx), XWEnv xwe )
 #define DW BONUS_DOUBLE_WORD
 #define TL BONUS_TRIPLE_LETTER
 #define TW BONUS_TRIPLE_WORD
+#define QL BONUS_QUAD_LETTER
+#define QW BONUS_QUAD_WORD
 
 static XWBonusType*
 bonusesFor( XP_U16 boardSize, XP_U16* len )
 {
-    static XWBonusType scrabbleBoard[] = { 
+    static XWBonusType scrabbleBoard[] = {
         TW,//EM,EM,DL,EM,EM,EM,TW,
         EM,DW,//EM,EM,EM,TL,EM,EM,
 
@@ -133,7 +135,7 @@ bonusesFor( XP_U16 boardSize, XP_U16* len )
         TW,EM,EM,DL,EM,EM,EM,DW,
     }; /* scrabbleBoard */
 
-    static XWBonusType seventeen[] = { 
+    static XWBonusType seventeen[] = {
         TW,//EM,EM,DL,EM,EM,EM,TW,
         EM,DW,//EM,EM,EM,TL,EM,EM,
 
@@ -146,17 +148,37 @@ bonusesFor( XP_U16 boardSize, XP_U16* len )
         EM,EM,DL,EM,EM,EM,DL,//EM,
         TW,EM,EM,DL,EM,EM,EM,DW,
         TW,EM,EM,DL,EM,EM,EM,DW,DW,
-    }; /* scrabbleBoard */
+    }; /* seventeen */
+
+    static XWBonusType twentyOne[] = {
+        QW,
+        EM, DW,
+        EM, EM, DW,
+        DL, EM, EM, TW,
+        EM, TL, EM, EM, DW,
+        EM, EM, QL, EM, EM, DW,
+        EM, EM, EM, DL, EM, EM, DW,
+        TW, EM, EM, EM, EM, EM, EM, DW,
+        EM, DW, EM, EM, TL, EM, EM, EM, TL,
+        EM, EM, DW, EM, EM, DL, EM, EM, EM, DL,
+        DL, EM, EM, TW, EM, EM, DL, EM, EM, EM, DW,
+    }; /* twentyOne */
 
     XWBonusType* result = NULL;
-    if ( boardSize == 15 ) {
+    switch ( boardSize ) {
+    case 15:
         result = scrabbleBoard;
         *len = VSIZE(scrabbleBoard);
-    } else if ( boardSize == 17 ) {
+        break;
+    case 17:
         result = seventeen;
         *len = VSIZE(seventeen);
+        break;
+    case 21:
+        result = twentyOne;
+        *len = VSIZE(twentyOne);
+        break;
     }
-
     return result;
 }