diff --git a/qw_client/screen.c b/qw_client/screen.c
index 20a0fdc..260fee0 100644
--- a/qw_client/screen.c
+++ b/qw_client/screen.c
@@ -268,7 +268,7 @@ float CalcFov (float fov_x, float width, float height)
 
         x = width/tan(fov_x/360*M_PI);
 
-        a = atan (height/x);
+        a = (x == 0) ? 90 : atan(height/x);
 
         a = a*360/M_PI;
 
diff --git a/uquake/screen.c b/uquake/screen.c
index 408e608..4bd9792 100644
--- a/uquake/screen.c
+++ b/uquake/screen.c
@@ -273,7 +273,7 @@ float CalcFov (float fov_x, float width, float height)
 
         x = width/tan(fov_x/360*M_PI);
 
-        a = atan (height/x);
+        a = (x == 0) ? 90 : atan(height/x);
 
         a = a*360/M_PI;