diff --git a/types/js.spec/index.d.ts b/types/js.spec/index.d.ts
index 735de40976..764bfa845e 100644
--- a/types/js.spec/index.d.ts
+++ b/types/js.spec/index.d.ts
@@ -71,7 +71,7 @@ export interface Problem {
  * @param value the value to test
  * @returns true if valid
  */
-export function valid(spec: Spec, value: any): boolean;
+export function valid(spec: spec.SpecInput, value: any): boolean;
 
 /**
  * Returns the conformed value to this spec.
@@ -79,7 +79,7 @@ export function valid(spec: Spec, value: any): boolean;
  * @param value the value to test
  * @returns if the value does not conform to the spec, or the conformed value if it does.
  */
-export function conform(spec: Spec, value: any): any;
+export function conform(spec: spec.SpecInput, value: any): any;
 
 /**
  * Like explain(), but returns Problems array.
@@ -87,28 +87,28 @@ export function conform(spec: Spec, value: any): any;
  * @param value the value to test
  * @returns list of problems or null if none
  */
-export function explainData(spec: Spec, value: any): Problem[];
+export function explainData(spec: spec.SpecInput, value: any): Problem[];
 
 /**
  * Prints, to the console, reasons why the value did not conform to this spec.
  * @param spec the spec to test with
  * @param value the value to test
  */
-export function explain(spec: Spec, value: any): void;
+export function explain(spec: spec.SpecInput, value: any): void;
 
 /**
  * Returns a multiline string with reasons why the value did not conform to this spec.
  * @param spec the spec to test with
  * @param value the value to test
  */
-export function explainStr(spec: Spec, value: any): string;
+export function explainStr(spec: spec.SpecInput, value: any): string;
 
 /**
  * Tests if a value conforms to a spec, and if not, throws an Error.
  * @param spec the spec to test with
  * @param value the value to test
  */
-export function assert(spec: Spec, value: any): void;
+export function assert(spec: spec.SpecInput, value: any): void;
 
 export namespace symbol {
     /**
diff --git a/types/js.spec/js.spec-tests.ts b/types/js.spec/js.spec-tests.ts
index 8bb9611e87..e1d7703f76 100644
--- a/types/js.spec/js.spec-tests.ts
+++ b/types/js.spec/js.spec-tests.ts
@@ -7,20 +7,28 @@ const name: string = spec.name;
 const options: object = spec.options;
 
 const isValid: boolean = S.valid(S.spec.boolean, true);
+S.valid((value) => true, "a value");
 
 const result = S.conform(S.spec.map("dancing", {field: S.spec.string}), "not a map");
+S.conform((value) => true, "a value");
 
 const problems: S.Problem[] = S.explainData(S.spec.int, "not a number");
+S.explainData((value) => true, "a value");
 
 const {path, via, value, predicate}: {path: string[], via: string[], value: any, predicate: S.Predicate} = problems[0];
 
 const problemStr: string = S.explainStr(S.spec.even, 3);
+S.explainStr((value) => true, "a value");
 
 // $ExpectType void
 S.explain(S.spec.positive, true);
+// $ExpectType void
+S.explain((value) => true, "a value");
 
 // $ExpectType void
 S.assert(S.spec.string, "things");
+// $ExpectType void
+S.assert((value) => true, "a value");
 
 const symbols: symbol[] = [S.symbol.count, S.symbol.invalid, S.symbol.maxCount, S.symbol.minCount, S.symbol.optional];