diff --git a/src/__tests__/number.test.js b/src/__tests__/number.test.js
index 802c87c2..257dc087 100644
--- a/src/__tests__/number.test.js
+++ b/src/__tests__/number.test.js
@@ -7,7 +7,7 @@ import { INPUTS } from './fixtures';
 
 describe('number', () => {
     const decoder = number;
-    const [okay, not_okay] = partition(INPUTS, Number.isFinite);
+    const [okay, not_okay] = partition(INPUTS, (n) => Number.isFinite(n));
 
     it('valid', () => {
         expect(okay.length).not.toBe(0);
@@ -48,7 +48,7 @@ describe('positiveNumber', () => {
 
 describe('integer', () => {
     const decoder = integer;
-    const [okay, not_okay] = partition(INPUTS, Number.isInteger);
+    const [okay, not_okay] = partition(INPUTS, (n) => Number.isInteger(n));
 
     it('valid', () => {
         expect(okay.length).not.toBe(0);
diff --git a/src/number.js b/src/number.js
index 4bf127f9..0f7840e8 100644
--- a/src/number.js
+++ b/src/number.js
@@ -12,9 +12,12 @@ const anyNumber: Decoder<number> = (blob: mixed) => {
         : Err(annotate(blob, 'Must be number'));
 };
 
+const isInteger = (n: number) => Number.isInteger(n);
+const isFinite = (n: number) => Number.isFinite(n);
+
 export const number: Decoder<number> = compose(
     anyNumber,
-    predicate(Number.isFinite, 'Number must be finite')
+    predicate(isFinite, 'Number must be finite')
 );
 export const positiveNumber: Decoder<number> = compose(
     number,
@@ -24,9 +27,9 @@ export const positiveNumber: Decoder<number> = compose(
 // Integers
 export const integer: Decoder<number> = compose(
     number,
-    predicate(Number.isInteger, 'Number must be an integer')
+    predicate(isInteger, 'Number must be an integer')
 );
 export const positiveInteger: Decoder<number> = compose(
-    number,
-    predicate((n) => n >= 0 && Number.isInteger(n), 'Number must be an integer')
+    integer,
+    predicate((n) => n >= 0, 'Number must be positive')
 );