diff --git a/gopro_8:7/unfish_gopro_8:7.glsl b/gopro_8:7/unfish_gopro_8:7.glsl
index 5338fea..7e69cd3 100644
--- a/gopro_8:7/unfish_gopro_8:7.glsl
+++ b/gopro_8:7/unfish_gopro_8:7.glsl
@@ -20,7 +20,7 @@
 
 #define color_conversion
 #define texture_filtering
-//#define rotate_180
+#define rotate_180
 //#define debug_borders
 
 #undef highp // defined by Qt-OpenGl
@@ -67,7 +67,7 @@ vec2 equidistant_to_rectilinear(const in vec2 equidistant) {
     float rectilinear_radius = length(equidistant);
     float rectilinear_angle = atan(rectilinear_radius / rectilinear_focal_length);
     float equidistant_radius = rectilinear_angle * equidistant_focal_length;
-    return equidistant * (equidistant_radius / rectilinear_radius);
+    return equidistant * (equidistant_radius / (rectilinear_radius > 0.0 ? rectilinear_radius : 1.0));
 }
 
 // color space (https://en.wikipedia.org/wiki/Rec._709)
@@ -136,7 +136,6 @@ vec2 bilinear_params(const in vec2 coord, out vec2 a, out vec2 b, out vec2 c, ou
 
 vec3 texture_filter(const in vec2 y_coord) {
     vec2 a, b, c, d, f = bilinear_params(y_coord, a, b, c, d);
-
     float luminance = mix(
         mix(
             decode_luminance(texture2DRect(myTextureY, a).x),
@@ -147,9 +146,7 @@ vec3 texture_filter(const in vec2 y_coord) {
             decode_luminance(texture2DRect(myTextureY, d).x),
             f.x),
         f.y);
-
     f = bilinear_params(y_coord * 0.5, a, b, c, d);
-
     vec2 chroma = mix(
         mix(
             decode_chroma(vec2(texture2DRect(myTextureU, a).x, texture2DRect(myTextureV, a).x)),
@@ -160,7 +157,6 @@ vec3 texture_filter(const in vec2 y_coord) {
             decode_chroma(vec2(texture2DRect(myTextureU, d).x, texture2DRect(myTextureV, d).x)),
             f.x),
         f.y);
-
     return vec3(luminance, chroma);
 }