diff --git a/xwords4/common/model.c b/xwords4/common/model.c
index f6fc9fb49..e692c8545 100644
--- a/xwords4/common/model.c
+++ b/xwords4/common/model.c
@@ -90,7 +90,9 @@ model_make( MPFORMAL DictionaryCtxt* dict,
             XP_U16 nRows )
 {
     ModelCtxt* result;
-    XP_U16 size = sizeof(*result) + TILES_SIZE(result, nCols);
+    XP_U16 size;
+    XP_ASSERT( nCols == nRows && nCols <= MAX_COLS );
+    size = sizeof(*result) + TILES_SIZE(result, nCols);
     result = (ModelCtxt*)XP_MALLOC( mpool, size );
     if ( result != NULL ) {
         XP_MEMSET( result, 0, sizeof(*result) );
@@ -700,15 +702,11 @@ setModelTileRaw( ModelCtxt* model, XP_U16 col, XP_U16 row, CellTile tile )
 static CellTile 
 getModelTileRaw( const ModelCtxt* model, XP_U16 col, XP_U16 row )
 {
-    CellTile tile;
     XP_U16 nCols = model->nCols;
     XP_ASSERT( model->nRows == nCols );
-    if ( col < nCols && row < nCols ) {
-        tile = model->tiles[(row*nCols) + col];
-    } else {
-        tile = TILE_EMPTY_BIT;
-    }
-    return tile;
+    XP_ASSERT( col < nCols );
+    XP_ASSERT( row < nCols );
+    return model->tiles[(row*nCols) + col];
 } /* getModelTileRaw */
 
 static void
diff --git a/xwords4/common/mscore.c b/xwords4/common/mscore.c
index 4077f613c..1131b984a 100644
--- a/xwords4/common/mscore.c
+++ b/xwords4/common/mscore.c
@@ -318,10 +318,11 @@ static XP_Bool
 modelIsEmptyAt( const ModelCtxt* model, XP_U16 col, XP_U16 row )
 {
     Tile tile;
-    XP_Bool found;
-
-    found = model_getTile( model, col, row, XP_FALSE, -1, &tile,
-                           NULL, NULL, NULL );
+    XP_U16 nCols = model_numCols( model );
+    XP_Bool found = col < nCols 
+        && row < nCols 
+        && model_getTile( model, col, row, XP_FALSE, -1, &tile, 
+                          NULL, NULL, NULL );
     return !found;
 } /* modelIsEmptyAt */
 
@@ -722,11 +723,12 @@ find_end( const ModelCtxt* model, XP_U16 col, XP_U16 row,
           XP_Bool isHorizontal ) 
 {
     XP_U16* incr = isHorizontal? &col: &row;
-    XP_U16 limit = isHorizontal? MAX_COLS-1:MAX_ROWS-1;
+    XP_U16 nCols = model_numCols( model );
+    XP_U16 limit = nCols - 1;
     XP_U16 lastGood = *incr;
 
-    XP_ASSERT( col < MAX_COLS );
-    XP_ASSERT( row < MAX_ROWS );
+    XP_ASSERT( col < nCols );
+    XP_ASSERT( row < nCols );
 
     for ( ; ; ) {
         XP_ASSERT( *incr <= limit );