diff --git a/src/curry.js b/src/curry.js
index a26d74d..96c53c4 100644
--- a/src/curry.js
+++ b/src/curry.js
@@ -1,9 +1,9 @@
-import { isInteger } from '@fpc/types';
+import { isInteger, expectFunction } from '@fpc/types';
 import { curry as unsafeCurry } from './internals';
 import { failWith } from './failWith';
 
 export const curry = (fn, numArgs = fn.length) => (
   isInteger(numArgs) && numArgs > 0
-    ? unsafeCurry(fn, numArgs)
+    ? unsafeCurry(expectFunction(fn), numArgs)
     : failWith(new TypeError(`Expected positive integer, got ${numArgs}`))
 );
diff --git a/src/flip.js b/src/flip.js
index 455dfb4..f58a6bb 100644
--- a/src/flip.js
+++ b/src/flip.js
@@ -1 +1,6 @@
-export const flip = fn => (...args) => fn(...args.reverse());
+import { expectFunction } from '@fpc/types';
+
+export const flip = fn => (
+  /* eslint-disable no-sequences */
+  expectFunction(fn), (...args) => fn(...args.reverse())
+);
diff --git a/src/lazy.js b/src/lazy.js
index 71704eb..85dd2ee 100644
--- a/src/lazy.js
+++ b/src/lazy.js
@@ -1,6 +1,10 @@
+import { expectFunction } from '@fpc/types';
+
 const empty = {};
 
 export const lazy = (fn, ...args) => {
+  expectFunction(fn);
+
   let result = empty;
 
   const cached = () => (
diff --git a/src/negate.js b/src/negate.js
index 402da2a..6ebb4fc 100644
--- a/src/negate.js
+++ b/src/negate.js
@@ -1 +1,6 @@
-export const negate = fn => (...args) => !fn(...args);
+import { expectFunction } from '@fpc/types';
+
+export const negate = fn => (
+  /* eslint-disable no-sequences */
+  expectFunction(fn), (...args) => !fn(...args)
+);