diff --git a/intern/cycles/integrator/pass_accessor.cpp b/intern/cycles/integrator/pass_accessor.cpp
index 4479442df56..9fa5aab9ea9 100644
--- a/intern/cycles/integrator/pass_accessor.cpp
+++ b/intern/cycles/integrator/pass_accessor.cpp
@@ -141,6 +141,7 @@ bool PassAccessor::get_render_tile_pixels(const RenderBuffers *render_buffers,
   const PassType type = pass_access_info_.type;
   const PassMode mode = pass_access_info_.mode;
   const PassInfo pass_info = Pass::get_info(type, pass_access_info_.include_albedo);
+  int num_written_components = pass_info.num_components;
 
   if (pass_info.num_components == 1) {
     /* Single channel passes. */
@@ -188,8 +189,10 @@ bool PassAccessor::get_render_tile_pixels(const RenderBuffers *render_buffers,
     else if ((pass_info.divide_type != PASS_NONE || pass_info.direct_type != PASS_NONE ||
               pass_info.indirect_type != PASS_NONE) &&
              mode != PassMode::DENOISED) {
-      /* RGB lighting passes that need to divide out color and/or sum direct and indirect. */
+      /* RGB lighting passes that need to divide out color and/or sum direct and indirect.
+       * These can also optionally write alpha like the combined pass. */
       get_pass_light_path(render_buffers, buffer_params, destination);
+      num_written_components = 4;
     }
     else {
       /* Passes that need no special computation, or denoised passes that already
@@ -215,7 +218,7 @@ bool PassAccessor::get_render_tile_pixels(const RenderBuffers *render_buffers,
     }
   }
 
-  pad_pixels(buffer_params, destination, pass_info.num_components);
+  pad_pixels(buffer_params, destination, num_written_components);
 
   return true;
 }
diff --git a/intern/cycles/kernel/film/read.h b/intern/cycles/kernel/film/read.h
index 18a593a75b1..ba895fd8909 100644
--- a/intern/cycles/kernel/film/read.h
+++ b/intern/cycles/kernel/film/read.h
@@ -214,6 +214,21 @@ ccl_device_inline void film_get_pass_pixel_light_path(
   pixel[0] = f.x;
   pixel[1] = f.y;
   pixel[2] = f.z;
+
+  /* Optional alpha channel. */
+  if (kfilm_convert->num_components >= 4) {
+    if (kfilm_convert->pass_combined != PASS_UNUSED) {
+      float scale, scale_exposure;
+      film_get_scale_and_scale_exposure(kfilm_convert, buffer, &scale, &scale_exposure);
+
+      ccl_global const float *in_combined = buffer + kfilm_convert->pass_combined;
+      const float alpha = in_combined[3] * scale;
+      pixel[3] = film_transparency_to_alpha(alpha);
+    }
+    else {
+      pixel[3] = 1.0f;
+    }
+  }
 }
 
 ccl_device_inline void film_get_pass_pixel_float3(ccl_global const KernelFilmConvert *ccl_restrict