diff --git a/manimlib/shaders/surface/vert.glsl b/manimlib/shaders/surface/vert.glsl
index 96b85bf4..8937282a 100644
--- a/manimlib/shaders/surface/vert.glsl
+++ b/manimlib/shaders/surface/vert.glsl
@@ -11,8 +11,14 @@ out vec4 v_color;
 #INSERT get_unit_normal.glsl
 #INSERT finalize_color.glsl
 
+const float EPSILON = 1e-10;
+
 void main(){
     emit_gl_Position(point);
-    vec3 normal = cross(normalize(du_point - point), normalize(dv_point - point));
-    v_color = finalize_color(rgba, point, normalize(normal));
+    vec3 du = (du_point - point);
+    vec3 dv = (dv_point - point);
+    vec3 normal = cross(du, dv);
+    float mag = length(normal);
+    vec3 unit_normal = (mag < EPSILON) ? vec3(0, 0, sign(point.z)) : normal / mag;
+    v_color = finalize_color(rgba, point, unit_normal);
 }
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