diff --git a/packages/babel-types/README.md b/packages/babel-types/README.md
index a48301c15c..51b2183103 100644
--- a/packages/babel-types/README.md
+++ b/packages/babel-types/README.md
@@ -1553,7 +1553,7 @@ See also `t.isObjectTypeProperty(node, opts)` and `t.assertObjectTypeProperty(no
 
 Aliases: `Flow`, `UserWhitespacable`
 
- - `key`: `Identifier` (required)
+ - `key`: `Identifier | StringLiteral` (required)
  - `value`: `FlowType` (required)
  - `variance`: `Variance` (default: `null`)
  - `kind`: `"init" | "get" | "set"` (default: `null`)
diff --git a/packages/babel-types/src/definitions/flow.js b/packages/babel-types/src/definitions/flow.js
index cbd75c7775..3d658873ff 100644
--- a/packages/babel-types/src/definitions/flow.js
+++ b/packages/babel-types/src/definitions/flow.js
@@ -291,7 +291,7 @@ defineType("ObjectTypeProperty", {
   visitor: ["key", "value", "variance"],
   aliases: ["Flow", "UserWhitespacable"],
   fields: {
-    key: validateType("Identifier"),
+    key: validateType(["Identifier", "StringLiteral"]),
     value: validateType("FlowType"),
     kind: validate(assertOneOf("init", "get", "set")),
     static: validate(assertValueType("boolean")),