diff --git a/Changes.md b/Changes.md
index 1a3a37e..5070a0e 100644
--- a/Changes.md
+++ b/Changes.md
@@ -1,3 +1,8 @@
+3.0.0a5
+=======
+
+- Dockerfile : Set `OPTIX_ROOT_DIR` environment variable.
+
 3.0.0a4
 =======
 
diff --git a/Dockerfile b/Dockerfile
index 46a758d..d1a0330 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -85,3 +85,6 @@ ENV PYTHONPATH=
 # Inkscape 1.3.2 prints "Setting _INKSCAPE_GC=disable as a workaround for broken libgc"
 # every time it is run, so we set it ourselves to silence that
 ENV _INKSCAPE_GC="disable"
+
+# Make the Optix SDK available for Cycles builds.
+ENV OPTIX_ROOT_DIR=/usr/local/NVIDIA-OptiX-SDK-7.3.0
\ No newline at end of file
diff --git a/build.py b/build.py
index ffe5e36..be1ce09 100755
--- a/build.py
+++ b/build.py
@@ -118,7 +118,7 @@
 parser.add_argument(
 	"--docker-image-version",
 	dest = "dockerImageVersion",
-	default = "3.0.0a4",
+	default = "3.0.0a5",
 	help = "The Docker image tag to use for Docker builds."
 )