diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3f5f730..d4c7e79 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,8 +10,9 @@ and this project adheres to
 
 ### Fixed
 
-- Writes to the outside of the result texture end up back inside the texture
-  on some Intel GPUs on Linux. Now they are correctly discarded again.
+- Fixed bug where writes outside texture bounds ended up inside the texture
+  on some Intel GPUs on Linux
+- Fixed guide marking shader to compile on Linux and Intel GPUs
 
 ## 4.0.0 - 2021-08-25
 
diff --git a/src/haloray-core/resources/shaders/guide.glsl b/src/haloray-core/resources/shaders/guide.glsl
index 3577072..e4c36bb 100644
--- a/src/haloray-core/resources/shaders/guide.glsl
+++ b/src/haloray-core/resources/shaders/guide.glsl
@@ -25,8 +25,12 @@ uniform struct camera_t
 #define PROJECTION_ORTHOGRAPHIC 4
 
 const float PI = 3.1415926535;
-const float LINEWIDTHDEGREES = 0.25 / sqrt(camera.focalLength);
-const float LINEWIDTH = LINEWIDTHDEGREES * PI / 180.0;
+// The following constants cannot be set to
+// `const` because the value depends on a
+// shader uniform, and consts must be
+// initialized with a constant expression.
+float LINEWIDTHDEGREES = 0.25 / sqrt(camera.focalLength);
+float LINEWIDTH = LINEWIDTHDEGREES * PI / 180.0;
 
 vec2 planarToPolar(vec2 point)
 {