--- a/gfx/wr/webrender/res/brush_conic_gradient.glsl
+++ b/gfx/wr/webrender/res/brush_conic_gradient.glsl
@@ -109,18 +109,18 @@ Fragment conic_gradient_brush_fs() {
         pos.y = V_REPEATED_SIZE.y;
     }
 #else
     // Apply potential horizontal and vertical repetitions.
     vec2 pos = mod(V_POS, V_REPEATED_SIZE);
 #endif
 
     vec2 current_dir = pos - V_CENTER;
-    float current_angle = atan(current_dir.y, current_dir.x) + (PI / 2 - V_ANGLE);
-    float offset = mod(current_angle / (2 * PI), 1.0);
+    float current_angle = atan(current_dir.y, current_dir.x) + (PI / 2.0 - V_ANGLE);
+    float offset = mod(current_angle / (2.0 * PI), 1.0);
 
     vec4 color = sample_gradient(V_GRADIENT_ADDRESS,
                                  offset,
                                  V_GRADIENT_REPEAT);
 
 #ifdef WR_FEATURE_ALPHA_PASS
     color *= init_transform_fs(V_LOCAL_POS);
 #endif

--- a/gfx/wr/webrender/tests/angle_shader_validation.rs
+++ b/gfx/wr/webrender/tests/angle_shader_validation.rs
@@ -101,16 +101,20 @@ const SHADERS: &[Shader] = &[
         name: "brush_blend",
         features: BRUSH_FEATURES,
     },
     Shader {
         name: "brush_mix_blend",
         features: BRUSH_FEATURES,
     },
     Shader {
+        name: "brush_conic_gradient",
+        features: GRADIENT_FEATURES,
+    },
+    Shader {
         name: "brush_radial_gradient",
         features: GRADIENT_FEATURES,
     },
     Shader {
         name: "brush_linear_gradient",
         features: GRADIENT_FEATURES,
     },
     Shader {