diff --git a/README.md b/README.md
index d8d8a8e..19a4242 100644
--- a/README.md
+++ b/README.md
@@ -294,6 +294,25 @@ type T = [/** foo */ number, /** bar */ string];
 The downlevel semantics are exactly the same as the original, but
 the TypeScript language service won't be able to show the member names.
 
+### `{ [key: T]: A }` (4.4)
+
+Typescript 4.4 supports template literals as index signature types:
+
+```ts
+type O = { [key: `ak${string}`]: A };
+```
+
+becomes
+
+```ts
+type O = { [key: string]: A };
+```
+
+#### Semantics
+
+The downlevel d.ts will be less strict because an index signature would
+have a more general type (`string`) instead of the original template literal type.
+
 ### `in out T` (4.7)
 
 Typescript 4.7 supports variance annotations on type parameter declarations:
diff --git a/baselines/reference/ts3.4/test.d.ts b/baselines/reference/ts3.4/test.d.ts
index dd58496..5b093ab 100644
--- a/baselines/reference/ts3.4/test.d.ts
+++ b/baselines/reference/ts3.4/test.d.ts
@@ -71,3 +71,6 @@ export declare const foo: {
 export type IR = IteratorResult<number>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = string;
+export type TTemplateLiteralIndexSignature = {
+    [key: string]: number;
+};
diff --git a/baselines/reference/ts3.5/test.d.ts b/baselines/reference/ts3.5/test.d.ts
index ae9928a..9e0fe74 100644
--- a/baselines/reference/ts3.5/test.d.ts
+++ b/baselines/reference/ts3.5/test.d.ts
@@ -71,3 +71,6 @@ export declare const foo: {
 export type IR = IteratorResult<number>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = string;
+export type TTemplateLiteralIndexSignature = {
+    [key: string]: number;
+};
diff --git a/baselines/reference/ts3.6/test.d.ts b/baselines/reference/ts3.6/test.d.ts
index 5b3a6f1..d006e46 100644
--- a/baselines/reference/ts3.6/test.d.ts
+++ b/baselines/reference/ts3.6/test.d.ts
@@ -73,3 +73,6 @@ export declare const foo: {
 export type IR = IteratorResult<number, string>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = string;
+export type TTemplateLiteralIndexSignature = {
+    [key: string]: number;
+};
diff --git a/baselines/reference/ts3.7/test.d.ts b/baselines/reference/ts3.7/test.d.ts
index 89d6270..ae77f31 100644
--- a/baselines/reference/ts3.7/test.d.ts
+++ b/baselines/reference/ts3.7/test.d.ts
@@ -73,3 +73,6 @@ export declare const foo: {
 export type IR = IteratorResult<number, string>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = string;
+export type TTemplateLiteralIndexSignature = {
+    [key: string]: number;
+};
diff --git a/baselines/reference/ts3.8/test.d.ts b/baselines/reference/ts3.8/test.d.ts
index f3b3ef8..b8ca6fe 100644
--- a/baselines/reference/ts3.8/test.d.ts
+++ b/baselines/reference/ts3.8/test.d.ts
@@ -74,3 +74,6 @@ export declare const foo: {
 export type IR = IteratorResult<number, string>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = string;
+export type TTemplateLiteralIndexSignature = {
+    [key: string]: number;
+};
diff --git a/baselines/reference/ts3.9/test.d.ts b/baselines/reference/ts3.9/test.d.ts
index f3b3ef8..b8ca6fe 100644
--- a/baselines/reference/ts3.9/test.d.ts
+++ b/baselines/reference/ts3.9/test.d.ts
@@ -74,3 +74,6 @@ export declare const foo: {
 export type IR = IteratorResult<number, string>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = string;
+export type TTemplateLiteralIndexSignature = {
+    [key: string]: number;
+};
diff --git a/baselines/reference/ts4.0/test.d.ts b/baselines/reference/ts4.0/test.d.ts
index ca58587..bdac74b 100644
--- a/baselines/reference/ts4.0/test.d.ts
+++ b/baselines/reference/ts4.0/test.d.ts
@@ -74,3 +74,6 @@ export declare const foo: {
 export type IR = IteratorResult<number, string>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = string;
+export type TTemplateLiteralIndexSignature = {
+    [key: string]: number;
+};
diff --git a/baselines/reference/ts4.1/test.d.ts b/baselines/reference/ts4.1/test.d.ts
index 3810eea..7c14621 100644
--- a/baselines/reference/ts4.1/test.d.ts
+++ b/baselines/reference/ts4.1/test.d.ts
@@ -74,3 +74,6 @@ export declare const foo: {
 export type IR = IteratorResult<number, string>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = `${string}abc${string}`;
+export type TTemplateLiteralIndexSignature = {
+    [key: string]: number;
+};
diff --git a/baselines/reference/ts4.2/test.d.ts b/baselines/reference/ts4.2/test.d.ts
index 3810eea..7c14621 100644
--- a/baselines/reference/ts4.2/test.d.ts
+++ b/baselines/reference/ts4.2/test.d.ts
@@ -74,3 +74,6 @@ export declare const foo: {
 export type IR = IteratorResult<number, string>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = `${string}abc${string}`;
+export type TTemplateLiteralIndexSignature = {
+    [key: string]: number;
+};
diff --git a/baselines/reference/ts4.3/test.d.ts b/baselines/reference/ts4.3/test.d.ts
index 3810eea..7c14621 100644
--- a/baselines/reference/ts4.3/test.d.ts
+++ b/baselines/reference/ts4.3/test.d.ts
@@ -74,3 +74,6 @@ export declare const foo: {
 export type IR = IteratorResult<number, string>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = `${string}abc${string}`;
+export type TTemplateLiteralIndexSignature = {
+    [key: string]: number;
+};
diff --git a/baselines/reference/ts4.4/test.d.ts b/baselines/reference/ts4.4/test.d.ts
index 3810eea..1338cfc 100644
--- a/baselines/reference/ts4.4/test.d.ts
+++ b/baselines/reference/ts4.4/test.d.ts
@@ -74,3 +74,6 @@ export declare const foo: {
 export type IR = IteratorResult<number, string>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = `${string}abc${string}`;
+export type TTemplateLiteralIndexSignature = {
+    [key: `${string}abc${string}`]: number;
+};
diff --git a/baselines/reference/ts4.5/test.d.ts b/baselines/reference/ts4.5/test.d.ts
index 82292d4..c2c7159 100644
--- a/baselines/reference/ts4.5/test.d.ts
+++ b/baselines/reference/ts4.5/test.d.ts
@@ -71,3 +71,6 @@ export declare const foo: {
 export type IR = IteratorResult<number, string>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = `${string}abc${string}`;
+export type TTemplateLiteralIndexSignature = {
+    [key: `${string}abc${string}`]: number;
+};
diff --git a/baselines/reference/ts4.6/test.d.ts b/baselines/reference/ts4.6/test.d.ts
index 82292d4..c2c7159 100644
--- a/baselines/reference/ts4.6/test.d.ts
+++ b/baselines/reference/ts4.6/test.d.ts
@@ -71,3 +71,6 @@ export declare const foo: {
 export type IR = IteratorResult<number, string>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = `${string}abc${string}`;
+export type TTemplateLiteralIndexSignature = {
+    [key: `${string}abc${string}`]: number;
+};
diff --git a/baselines/reference/ts4.7/test.d.ts b/baselines/reference/ts4.7/test.d.ts
index 82292d4..c2c7159 100644
--- a/baselines/reference/ts4.7/test.d.ts
+++ b/baselines/reference/ts4.7/test.d.ts
@@ -71,3 +71,6 @@ export declare const foo: {
 export type IR = IteratorResult<number, string>;
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = `${string}abc${string}`;
+export type TTemplateLiteralIndexSignature = {
+    [key: `${string}abc${string}`]: number;
+};
diff --git a/index.js b/index.js
index 5fd4338..c2f3f41 100644
--- a/index.js
+++ b/index.js
@@ -367,6 +367,26 @@ function doTransform(checker, targetVersion, k) {
         ts.unescapeLeadingUnderscores(member.name.escapedText),
         /*hasTrailingNewline*/ false
       );
+    } else if (
+        semver.lt(targetVersion, "4.4.0") &&
+        ts.isIndexSignatureDeclaration(n) &&
+        ts.SyntaxKind.TemplateLiteralType === n.parameters[0].type.kind
+    ) {
+      const [p] = n.parameters;
+      return ts.factory.createIndexSignature(
+        n.modifiers,
+        [
+          ts.factory.createParameterDeclaration(
+            p.modifiers,
+            p.dotDotDotToken,
+            p.name,
+            p.questionToken,
+            ts.factory.createKeywordTypeNode(ts.SyntaxKind.StringKeyword),
+            p.initializer
+          )
+        ],
+        n.type
+      );
     } else if (semver.lt(targetVersion, "4.7.0") && ts.isTypeParameterDeclaration(n)) {
       return ts.factory.createTypeParameterDeclaration(
         n.modifiers?.filter(
diff --git a/test/test.d.ts b/test/test.d.ts
index 7d516f4..dabdf6d 100644
--- a/test/test.d.ts
+++ b/test/test.d.ts
@@ -78,3 +78,5 @@ export type IR = IteratorResult<number, string>;
 
 /** Template Literal - supported since 4.1 < should be StringKeyword */
 export type TTemplateLiteral = `${string}abc${string}`;
+
+export type TTemplateLiteralIndexSignature = { [key: `${string}abc${string}`]: number }