diff --git a/src/terraform_gui.cpp b/src/terraform_gui.cpp
--- a/src/terraform_gui.cpp
+++ b/src/terraform_gui.cpp
@@ -107,16 +107,16 @@ bool GUIPlaceProcDragXY(ViewportDragDrop
 
 	switch (proc) {
 		case DDSP_DEMOLISH_AREA:
-			DoCommandP(end_tile, start_tile, _ctrl_pressed, CMD_CLEAR_AREA | CMD_MSG(STR_ERROR_CAN_T_CLEAR_THIS_AREA), CcPlaySound10);
+			DoCommandP(end_tile, start_tile, _ctrl_pressed ? 1 : 0, CMD_CLEAR_AREA | CMD_MSG(STR_ERROR_CAN_T_CLEAR_THIS_AREA), CcPlaySound10);
 			break;
 		case DDSP_RAISE_AND_LEVEL_AREA:
-			DoCommandP(end_tile, start_tile, LM_RAISE << 1 | _ctrl_pressed, CMD_LEVEL_LAND | CMD_MSG(STR_ERROR_CAN_T_RAISE_LAND_HERE), CcTerraform);
+			DoCommandP(end_tile, start_tile, LM_RAISE << 1 | (_ctrl_pressed ? 1 : 0), CMD_LEVEL_LAND | CMD_MSG(STR_ERROR_CAN_T_RAISE_LAND_HERE), CcTerraform);
 			break;
 		case DDSP_LOWER_AND_LEVEL_AREA:
-			DoCommandP(end_tile, start_tile, LM_LOWER << 1 | _ctrl_pressed, CMD_LEVEL_LAND | CMD_MSG(STR_ERROR_CAN_T_LOWER_LAND_HERE), CcTerraform);
+			DoCommandP(end_tile, start_tile, LM_LOWER << 1 | (_ctrl_pressed ? 1 : 0), CMD_LEVEL_LAND | CMD_MSG(STR_ERROR_CAN_T_LOWER_LAND_HERE), CcTerraform);
 			break;
 		case DDSP_LEVEL_AREA:
-			DoCommandP(end_tile, start_tile, LM_LEVEL << 1 | _ctrl_pressed, CMD_LEVEL_LAND | CMD_MSG(STR_ERROR_CAN_T_LEVEL_LAND_HERE), CcTerraform);
+			DoCommandP(end_tile, start_tile, LM_LEVEL << 1 | (_ctrl_pressed ? 1 : 0), CMD_LEVEL_LAND | CMD_MSG(STR_ERROR_CAN_T_LEVEL_LAND_HERE), CcTerraform);
 			break;
 		case DDSP_CREATE_ROCKS:
 			GenerateRockyArea(end_tile, start_tile);
diff --git a/src/viewport.cpp b/src/viewport.cpp
--- a/src/viewport.cpp
+++ b/src/viewport.cpp
@@ -1764,8 +1764,8 @@ static void SetSelectionTilesDirty()
 		/* a_size, b_size describe a rectangle with rotated coordinates */
 		int a_size = x_size + y_size, b_size = x_size - y_size;
 
-		int interval_a = a_size < 0 ? -TILE_SIZE : TILE_SIZE;
-		int interval_b = b_size < 0 ? -TILE_SIZE : TILE_SIZE;
+		int interval_a = a_size < 0 ? -(int)TILE_SIZE : TILE_SIZE;
+		int interval_b = b_size < 0 ? -(int)TILE_SIZE : TILE_SIZE;
 
 		for (int a = -interval_a; a != a_size + interval_a; a += interval_a) {
 			for (int b = -interval_b; b != b_size + interval_b; b += interval_b) {