diff --git a/README.md b/README.md
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--- a/README.md
+++ b/README.md
@@ -297,7 +297,7 @@ It can also function against the chat completion endpoint provided by <a href="h
 
 Variable | Purpose
 -------- | -------
-GRIST_SANDBOX_FLAVOR | can be pynbox, unsandboxed, docker, or macSandboxExec. If set, forces Grist to use the specified kind of sandbox.
+GRIST_SANDBOX_FLAVOR | can be gvisor, pynbox, unsandboxed, docker, or macSandboxExec. If set, forces Grist to use the specified kind of sandbox.
 GRIST_SANDBOX | a program or image name to run as the sandbox. See NSandbox.ts for nerdy details.
 PYTHON_VERSION | can be 2 or 3. If set, documents without an engine setting are assumed to use the specified version of python. Not all sandboxes support all versions.
 PYTHON_VERSION_ON_CREATION | can be 2 or 3. If set, newly created documents have an engine setting set to python2 or python3. Not all sandboxes support all versions.