diff --git a/output.png b/output.png
index a921ad4..e498248 100644
Binary files a/output.png and b/output.png differ
diff --git a/scenes/scene5.json b/scenes/scene5.json
index aa290a3..ca77857 100644
--- a/scenes/scene5.json
+++ b/scenes/scene5.json
@@ -28,5 +28,14 @@
 	    "diffuse": [0.0, 0.5, 1.0],
 	    "specular": [0.0, 0.0, 0.0]
 	}
+    },
+
+    "disk": {
+	"position": [-1.0, 0.0, -3.0],
+	"normal": [1.0, 0.0, 1.0],
+	"radius": 3.0,
+	"material": {
+	    "diffuse": [1.0, 0.5, 0.0]
+	}
     }
 }
diff --git a/tracer.cpp b/tracer.cpp
index 56465c0..84e1554 100644
--- a/tracer.cpp
+++ b/tracer.cpp
@@ -11,7 +11,9 @@ const vec3 BCKG_COLOR = vec3(0.1f);
 float Tracer::fresnel(const vec3 & i, const vec3 & n, const float ir1, const float ir2) const {
   float cos_t1 = dot(i, n);
   float cos_t2 = dot(normalize(refract(i, n, ir1 / ir2)), n);
-  float sin_t2 = (ir1 / ir2) * glm::sqrt(1.0f - (cos_t2 * cos_t2));
+  float cos_t2s = (cos_t2 * cos_t2);
+  cos_t2s = cos_t2s > 1.0f ? 1.0 : cos_t2s;
+  float sin_t2 = (ir1 / ir2) * glm::sqrt(1.0f - cos_t2s);
 
   if (sin_t2 >= 1.0f)
     return 1.0f;