diff --git a/source_files/edge/r_sky.cc b/source_files/edge/r_sky.cc
index 5fe49a6a0..113fa820f 100644
--- a/source_files/edge/r_sky.cc
+++ b/source_files/edge/r_sky.cc
@@ -259,11 +259,11 @@ static void SetupSkyMatrices(void)
         glLoadIdentity();
 
         if (fliplevels.d_)
-            glFrustum(-view_x_slope * renderer_near_clip.f_, view_x_slope * renderer_near_clip.f_,
+            glFrustum(view_x_slope * renderer_near_clip.f_, -view_x_slope * renderer_near_clip.f_,
                     -view_y_slope * renderer_near_clip.f_, view_y_slope * renderer_near_clip.f_, renderer_near_clip.f_,
                     renderer_far_clip.f_ * 4.0);
         else
-            glFrustum(view_x_slope * renderer_near_clip.f_, -view_x_slope * renderer_near_clip.f_,
+            glFrustum(-view_x_slope * renderer_near_clip.f_, view_x_slope * renderer_near_clip.f_,
                     -view_y_slope * renderer_near_clip.f_, view_y_slope * renderer_near_clip.f_, renderer_near_clip.f_,
                     renderer_far_clip.f_ * 4.0);
 
@@ -272,7 +272,7 @@ static void SetupSkyMatrices(void)
         glLoadIdentity();
 
         glRotatef(270.0f - epi::DegreesFromBAM(view_vertical_angle), 1.0f, 0.0f, 0.0f);
-        glRotatef(epi::DegreesFromBAM(view_angle), 0.0f, 0.0f, 1.0f);
+        glRotatef(-epi::DegreesFromBAM(view_angle), 0.0f, 0.0f, 1.0f);
 
         if (current_sky_stretch == kSkyStretchStretch)
             glTranslatef(0.0f, 0.0f,