diff --git a/src/defs.h b/src/defs.h
index 18da025..6fbe540 100644
--- a/src/defs.h
+++ b/src/defs.h
@@ -755,8 +755,8 @@ const char * const systemBackground[] = {
 };
 
 const int rate2reload[6] = {15, 15, 13, 11, 9, 7};
-const int screenWidth = SCREEN_WIDTH;
-const int screenHeight = SCREEN_HEIGHT;
+const int screenWidth = MAX(SCREEN_WIDTH, 640);
+const int screenHeight = MAX(SCREEN_HEIGHT, 480);
 const int xViewBorder = 100;
 const int yViewBorder = 100;
 const float cameraMaxSpeed = 3.;
diff --git a/src/intermission.h b/src/intermission.h
index ab0a143..6ec1846 100644
--- a/src/intermission.h
+++ b/src/intermission.h
@@ -25,7 +25,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 extern Planet intermission_planets[MAX_PLANETS];
 
-const int intermission_ycenter = 50 + (SCREEN_HEIGHT - 150) / 2;
+const int intermission_ycenter = 50 + (screenHeight - 150) / 2;
 
 void intermission_initPlanets(int system);
 void intermission_unlockPlanets();
diff --git a/src/shop.cpp b/src/shop.cpp
index 48fb8e8..bbf682b 100644
--- a/src/shop.cpp
+++ b/src/shop.cpp
@@ -44,7 +44,7 @@ typedef struct ShopItem_ {
 } ShopItem;
 
 static const int shop_w = 600;
-static const int shop_x = SCREEN_WIDTH / 2 - shop_w / 2;
+static const int shop_x = screenWidth / 2 - shop_w / 2;
 static const int shop_h = 336;
 static const int shop_y = intermission_ycenter - shop_h / 2;