diff --git a/src/render/painter.js b/src/render/painter.js
index 924d59f8ba9..4bab2a9fba2 100644
--- a/src/render/painter.js
+++ b/src/render/painter.js
@@ -760,7 +760,7 @@ class Painter {
         // rendering. Removing the fog flag during tile rendering avoids additional defines.
         if (fog && !rtt) {
             defines.push('FOG');
-            if (haze) defines.push('HAZE');
+            if (haze) defines.push('FOG_HAZE');
         }
         if (rtt) defines.push('RENDER_TO_TEXTURE');
         if (this._showOverdrawInspector) defines.push('OVERDRAW_INSPECTOR');
diff --git a/src/shaders/_prelude_fog.fragment.glsl b/src/shaders/_prelude_fog.fragment.glsl
index 5fe7c57d520..1454c82d950 100644
--- a/src/shaders/_prelude_fog.fragment.glsl
+++ b/src/shaders/_prelude_fog.fragment.glsl
@@ -25,10 +25,11 @@ float fog_sky_blending(vec3 camera_dir) {
     return u_fog_opacity * exp(-3.0 * t * t);
 }
 
-// This function gives the fog opacity when strength is 1. Otherwise it's multiplied
+// Computes the fog opacity when fog strength = 1. Otherwise it's multiplied
 // by a smoothstep to a power to decrease the amount of fog relative to haze.
-// This function much match src/style/fog.js
+//   - t: depth, rescaled to 0 at fogStart and 1 at fogEnd
 // See: https://www.desmos.com/calculator/3taufutxid
+// This function much match src/style/fog.js
 float fog_opacity(float t) {
     const float decay = 6.0;
     float falloff = 1.0 - min(1.0, exp(-decay * t));
@@ -40,6 +41,8 @@ float fog_opacity(float t) {
     return u_fog_opacity * min(1.0, 1.00747 * falloff);
 }
 
+// This function is only used in rare places like heatmap where opacity is used
+// directly, outside the normal fog_apply method.
 float fog_opacity (vec3 pos) {
     return fog_opacity((length(pos) - u_fog_range.x) / (u_fog_range.y - u_fog_range.x));
 }
@@ -51,7 +54,7 @@ vec3 fog_apply(vec3 color, vec3 pos) {
     float haze_opac = fog_opacity(pos);
     float fog_opac = haze_opac * pow(smoothstep(0.0, 1.0, t), u_fog_exponent);
 
-#ifdef HAZE
+#ifdef FOG_HAZE
     vec3 haze = (haze_opac * u_haze_energy) * u_haze_color_linear;
 
     // The smoothstep fades in tonemapping slightly before the fog layer. This causes
diff --git a/src/style/fog.js b/src/style/fog.js
index a703eb817aa..20693005d90 100644
--- a/src/style/fog.js
+++ b/src/style/fog.js
@@ -77,8 +77,6 @@ export class FogSampler {
         // Account for fog strength
         falloff *= Math.pow(smoothstep(0, 1, t), fogExponent);
 
-        // We may wish to account for haze's effect on obscuring symbols
-
         return falloff * fogOpacity;
     }