diff --git a/CHANGELOG.md b/CHANGELOG.md
index a64d70e9f..e046ae8dd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # CHANGELOG
 
+## 2.12.2 Jun 1, 2020
+
+- Fix `isFunction` signature to assert `Function`
+
 ## 2.12.1 Jun 1, 2020
 
 - **Important** Removed `mnemonicToSeed`, it is only for bip39, use `mnemonicToMiniSecret` for the Substrate variant
diff --git a/lerna.json b/lerna.json
index c13e75211..59d1050d3 100644
--- a/lerna.json
+++ b/lerna.json
@@ -9,5 +9,5 @@
   "packages": [
     "packages/*"
   ],
-  "version": "2.12.1"
+  "version": "2.12.2"
 }
diff --git a/package.json b/package.json
index 6361192a8..044539289 100644
--- a/package.json
+++ b/package.json
@@ -26,5 +26,5 @@
     "@polkadot/ts": "^0.3.25",
     "@types/jest": "^25.2.3"
   },
-  "version": "2.12.1"
+  "version": "2.12.2"
 }
diff --git a/packages/keyring/package.json b/packages/keyring/package.json
index 915e4d39b..9b32555f3 100644
--- a/packages/keyring/package.json
+++ b/packages/keyring/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/keyring",
-  "version": "2.12.1",
+  "version": "2.12.2",
   "description": "Keyring management",
   "main": "index.js",
   "publishConfig": {
@@ -28,7 +28,7 @@
   "homepage": "https://github.com/polkadot-js/common/tree/master/packages/keyring#readme",
   "dependencies": {
     "@babel/runtime": "^7.9.6",
-    "@polkadot/util": "2.12.1",
-    "@polkadot/util-crypto": "2.12.1"
+    "@polkadot/util": "2.12.2",
+    "@polkadot/util-crypto": "2.12.2"
   }
 }
diff --git a/packages/util-crypto/package.json b/packages/util-crypto/package.json
index cb5f2b07b..88f542de7 100644
--- a/packages/util-crypto/package.json
+++ b/packages/util-crypto/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/util-crypto",
-  "version": "2.12.1",
+  "version": "2.12.2",
   "description": "A collection of useful crypto utilities for @polkadot",
   "main": "index.js",
   "keywords": [
@@ -26,7 +26,7 @@
   "homepage": "https://github.com/polkadot-js/common/tree/master/packages/util-crypto#readme",
   "dependencies": {
     "@babel/runtime": "^7.9.6",
-    "@polkadot/util": "2.12.1",
+    "@polkadot/util": "2.12.2",
     "@polkadot/wasm-crypto": "^1.2.1",
     "base-x": "^3.0.8",
     "bip39": "^3.0.2",
diff --git a/packages/util/package.json b/packages/util/package.json
index 552331cb9..a3523665a 100644
--- a/packages/util/package.json
+++ b/packages/util/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/util",
-  "version": "2.12.1",
+  "version": "2.12.2",
   "description": "A collection of useful utilities for @polkadot",
   "main": "index.js",
   "keywords": [
diff --git a/packages/util/src/is/function.ts b/packages/util/src/is/function.ts
index cd6eb1ee3..df000d666 100644
--- a/packages/util/src/is/function.ts
+++ b/packages/util/src/is/function.ts
@@ -2,7 +2,8 @@
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
 
-type FnType = (...params: unknown[]) => unknown;
+// eslint-disable-next-line @typescript-eslint/ban-types
+type FnType = Function;
 
 /**
  * @name isFunction
diff --git a/yarn.lock b/yarn.lock
index 9ac9dbe4b..5997f102f 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2758,8 +2758,8 @@ __metadata:
   resolution: "@polkadot/keyring@workspace:packages/keyring"
   dependencies:
     "@babel/runtime": ^7.9.6
-    "@polkadot/util": 2.12.1
-    "@polkadot/util-crypto": 2.12.1
+    "@polkadot/util": 2.12.2
+    "@polkadot/util-crypto": 2.12.2
   languageName: unknown
   linkType: soft
 
@@ -2772,12 +2772,12 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@polkadot/util-crypto@2.12.1, @polkadot/util-crypto@workspace:packages/util-crypto":
+"@polkadot/util-crypto@2.12.2, @polkadot/util-crypto@workspace:packages/util-crypto":
   version: 0.0.0-use.local
   resolution: "@polkadot/util-crypto@workspace:packages/util-crypto"
   dependencies:
     "@babel/runtime": ^7.9.6
-    "@polkadot/util": 2.12.1
+    "@polkadot/util": 2.12.2
     "@polkadot/wasm-crypto": ^1.2.1
     "@types/bn.js": ^4.11.6
     "@types/bs58": ^4.0.1
@@ -2797,7 +2797,7 @@ __metadata:
   languageName: unknown
   linkType: soft
 
-"@polkadot/util@2.12.1, @polkadot/util@workspace:packages/util":
+"@polkadot/util@2.12.2, @polkadot/util@workspace:packages/util":
   version: 0.0.0-use.local
   resolution: "@polkadot/util@workspace:packages/util"
   dependencies: