diff --git a/index.d.ts b/index.d.ts
index a1a8fa595..f9e18b8f7 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -122,7 +122,7 @@ export interface AssertAssertion {
 
 export interface DeepEqualAssertion {
 	/** Assert that `actual` is [deeply equal](https://github.com/concordancejs/concordance#comparison-details) to `expected`. */
-	<ValueType = any>(actual: ValueType, expected: ValueType, message?: string): void;
+	<ValueType = any, ValueType_ extends ValueType = ValueType>(actual: ValueType, expected: ValueType_, message?: string): void; // See #2575
 
 	/** Skip this assertion. */
 	skip(actual: any, expected: any, message?: string): void;
@@ -165,7 +165,7 @@ export interface IsAssertion {
 	 * Assert that `actual` is [the same
 	 * value](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is) as `expected`.
 	 */
-	<ValueType = any>(actual: ValueType, expected: ValueType, message?: string): void;
+	<ValueType = any, ValueType_ extends ValueType = ValueType>(actual: ValueType, expected: ValueType_, message?: string): void; // See #2575
 
 	/** Skip this assertion. */
 	skip(actual: any, expected: any, message?: string): void;
@@ -176,7 +176,7 @@ export interface NotAssertion {
 	 * Assert that `actual` is not [the same
 	 * value](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is) as `expected`.
 	 */
-	<ValueType = any>(actual: ValueType, expected: ValueType, message?: string): void;
+	<ValueType = any, ValueType_ extends ValueType = ValueType>(actual: ValueType, expected: ValueType_, message?: string): void; // See #2575
 
 	/** Skip this assertion. */
 	skip(actual: any, expected: any, message?: string): void;
@@ -184,7 +184,7 @@ export interface NotAssertion {
 
 export interface NotDeepEqualAssertion {
 	/** Assert that `actual` is not [deeply equal](https://github.com/concordancejs/concordance#comparison-details) to `expected`. */
-	<ValueType = any>(actual: ValueType, expected: ValueType, message?: string): void;
+	<ValueType = any, ValueType_ extends ValueType = ValueType>(actual: ValueType, expected: ValueType_, message?: string): void; // See #2575
 
 	/** Skip this assertion. */
 	skip(actual: any, expected: any, message?: string): void;
diff --git a/test-d/regression-2575.ts b/test-d/regression-2575.ts
new file mode 100644
index 000000000..6bc9b0d15
--- /dev/null
+++ b/test-d/regression-2575.ts
@@ -0,0 +1,16 @@
+import {expectError} from 'tsd';
+import {IsAssertion, NotAssertion, DeepEqualAssertion, NotDeepEqualAssertion} from '..';
+
+declare const is: IsAssertion;
+declare const not: NotAssertion;
+declare const deepEqual: DeepEqualAssertion;
+declare const notDeepEqual: NotDeepEqualAssertion;
+
+declare const literalStringUnionValue: 'hello' | 'world';
+declare const objectWithLiteralStringUnionValue: {foo: 'hello' | 'world'};
+
+// See #2575 and https://github.com/microsoft/TypeScript/issues/40377
+expectError(is(literalStringUnionValue, 'another-string'));
+expectError(not(literalStringUnionValue, 'another-string'));
+expectError(deepEqual(objectWithLiteralStringUnionValue, {foo: 'another-string'}));
+expectError(notDeepEqual(objectWithLiteralStringUnionValue, {foo: 'another-string'}));