diff --git a/docs/environment.md b/docs/environment.md
index b75757e..d43e1d0 100644
--- a/docs/environment.md
+++ b/docs/environment.md
@@ -74,6 +74,7 @@ An empty default means the variable is unset and its value is determined automat
 | `DISPLAY` | `none` | Display backend, such as `vnc`, `disabled`, or `none`. |
 | `VGA` | `none` | QEMU video adapter model. |
 | `GPU` | `N` | Enables GPU acceleration. |
+| `VRAM_SIZE` | `4G` | Virtual GPU memory budget. |
 | `RENDERNODE` | `/dev/dri/renderD128` | Render node used for GPU acceleration. |
 
 ## 🎈 Memory Ballooning