diff --git a/src/mol-gl/shader/chunks/common-frag-params.glsl.ts b/src/mol-gl/shader/chunks/common-frag-params.glsl.ts
index 290312d1c8fe74d6b57c6955a8123dce68b0a54e..6ee029edb1a3bcfda5866b7be472485185404ba4 100644
--- a/src/mol-gl/shader/chunks/common-frag-params.glsl.ts
+++ b/src/mol-gl/shader/chunks/common-frag-params.glsl.ts
@@ -5,7 +5,11 @@ uniform int uGroupCount;
 
 uniform vec3 uHighlightColor;
 uniform vec3 uSelectColor;
-varying float vMarker;
+#if __VERSION__ != 300
+    varying float vMarker;
+#else
+    flat in float vMarker;
+#endif
 
 varying vec3 vViewPosition;
 
diff --git a/src/mol-gl/shader/chunks/common-vert-params.glsl.ts b/src/mol-gl/shader/chunks/common-vert-params.glsl.ts
index da34156ae43c9d24f54bbfa3be2c6d9a7207a8cc..6354dc37db2529911b413422bfce27e7b0d46881 100644
--- a/src/mol-gl/shader/chunks/common-vert-params.glsl.ts
+++ b/src/mol-gl/shader/chunks/common-vert-params.glsl.ts
@@ -8,7 +8,11 @@ uniform int uGroupCount;
 
 uniform vec2 uMarkerTexDim;
 uniform sampler2D tMarker;
-varying float vMarker;
+#if __VERSION__ != 300
+    varying float vMarker;
+#else
+    flat out float vMarker;
+#endif
 
 varying vec3 vViewPosition;
 `
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