diff --git a/CHANGELOG.md b/CHANGELOG.md
index 92b9b0e..f934fe7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Unitflow changelog
 
+## 1.0.3 - 2024-01-19
+
+* Gracefully stop a flow when at least one unit inside it isn't a function, informing on console
+
 ## 1.0.2 - 2024-01-19
 
 * Updated how ESM and CommonJS versions are distributed
diff --git a/dist/unitflow.cjs b/dist/unitflow.cjs
index 48b74ec..eaaabfd 100644
--- a/dist/unitflow.cjs
+++ b/dist/unitflow.cjs
@@ -1 +1 @@
-"use strict";exports.Unitflow=class{constructor(e={}){this.unit={},this.flow={},this.state=e}async run(...e){const t=[],n=this.prepare(e);n.flows.reverse();for(let e=n.flows.length-1;e>=0;e--){const s=new Promise((t=>this.link_and_start(n.flows[e],n,t)));t.push(s)}return Promise.all(t)}prepare(e){let t=e.pop();const n={};return"string"==typeof t?(e.push(t),t={}):this.dependents(t,n),{flows:e,dependencies:t,dependents:n,execution:{}}}dependents(e,t){for(let[n,s]of Object.entries(e))for(let e=s.length-1;e>=0;e--)t[s[e]]||(t[s[e]]=[]),t[s[e]].push(n)}link_and_start(e,t,n){const s=this.flow[e],i=s.length,o={},r=this.state;for(let c=i-1;c>=0;c--){const d=this.unit[s[c]].bind(this),p=c==i-1?n:o[c+1],l=e+":"+s[c],h=async()=>d(r,p,n);o[c]=()=>this.wait_or_run(l,h,t)}o[0]()}wait_or_run(e,t,n,s=!1){if(!s&&!this.dependencies_completed(e,n))return n.execution[e]=()=>this.wait_or_run(e,t,n,!0);n.execution[e]=!0,t(),this.check_dependents(e,n)}dependencies_completed(e,t){const n=t.dependencies[e];return!n||n.every((e=>!0===t.execution[e]))}check_dependents(e,t){const n=t.dependents[e];if(n)for(let e=n.length-1;e>=0;e--){const s=n[e];"function"==typeof t.execution[s]&&(this.dependencies_completed(s,t)&&t.execution[s]())}}};
+"use strict";exports.Unitflow=class{constructor(e={}){this.unit={},this.flow={},this.state=e}async run(...e){const t=[],n=this.prepare(e);n.flows.reverse();for(let e=n.flows.length-1;e>=0;e--){const s=new Promise((t=>this.link_and_start(n.flows[e],n,t)));t.push(s)}return Promise.all(t)}prepare(e){let t=e.pop();const n={};return"string"==typeof t?(e.push(t),t={}):this.dependents(t,n),{flows:e,dependencies:t,dependents:n,execution:{}}}dependents(e,t){for(let[n,s]of Object.entries(e))for(let e=s.length-1;e>=0;e--)t[s[e]]||(t[s[e]]=[]),t[s[e]].push(n)}link_and_start(e,t,n){const s=this.flow[e],o=s.length,i={},r=this.state;for(let c=o-1;c>=0;c--){if("function"!=typeof this.unit[s[c]])return console.log(`Error: Unit "${s[c]}" on flow "${e}" is not a function. This flow execution is stopped.`)&&n();const d=this.unit[s[c]].bind(this),l=c==o-1?n:i[c+1],p=e+":"+s[c],u=async()=>d(r,l,n);i[c]=()=>this.wait_or_run(p,u,t)}i[0]()}wait_or_run(e,t,n,s=!1){if(!s&&!this.dependencies_completed(e,n))return n.execution[e]=()=>this.wait_or_run(e,t,n,!0);n.execution[e]=!0,t(),this.check_dependents(e,n)}dependencies_completed(e,t){const n=t.dependencies[e];return!n||n.every((e=>!0===t.execution[e]))}check_dependents(e,t){const n=t.dependents[e];if(n)for(let e=n.length-1;e>=0;e--){const s=n[e];"function"==typeof t.execution[s]&&(this.dependencies_completed(s,t)&&t.execution[s]())}}};
diff --git a/dist/unitflow.mjs b/dist/unitflow.mjs
index 333db32..eefb13e 100644
--- a/dist/unitflow.mjs
+++ b/dist/unitflow.mjs
@@ -1 +1 @@
-class e{constructor(e={}){this.unit={},this.flow={},this.state=e}async run(...e){const t=[],n=this.prepare(e);n.flows.reverse();for(let e=n.flows.length-1;e>=0;e--){const s=new Promise((t=>this.link_and_start(n.flows[e],n,t)));t.push(s)}return Promise.all(t)}prepare(e){let t=e.pop();const n={};return"string"==typeof t?(e.push(t),t={}):this.dependents(t,n),{flows:e,dependencies:t,dependents:n,execution:{}}}dependents(e,t){for(let[n,s]of Object.entries(e))for(let e=s.length-1;e>=0;e--)t[s[e]]||(t[s[e]]=[]),t[s[e]].push(n)}link_and_start(e,t,n){const s=this.flow[e],i=s.length,o={},r=this.state;for(let c=i-1;c>=0;c--){const d=this.unit[s[c]].bind(this),p=c==i-1?n:o[c+1],h=e+":"+s[c],l=async()=>d(r,p,n);o[c]=()=>this.wait_or_run(h,l,t)}o[0]()}wait_or_run(e,t,n,s=!1){if(!s&&!this.dependencies_completed(e,n))return n.execution[e]=()=>this.wait_or_run(e,t,n,!0);n.execution[e]=!0,t(),this.check_dependents(e,n)}dependencies_completed(e,t){const n=t.dependencies[e];return!n||n.every((e=>!0===t.execution[e]))}check_dependents(e,t){const n=t.dependents[e];if(n)for(let e=n.length-1;e>=0;e--){const s=n[e];"function"==typeof t.execution[s]&&(this.dependencies_completed(s,t)&&t.execution[s]())}}}export{e as Unitflow};
+class e{constructor(e={}){this.unit={},this.flow={},this.state=e}async run(...e){const t=[],n=this.prepare(e);n.flows.reverse();for(let e=n.flows.length-1;e>=0;e--){const s=new Promise((t=>this.link_and_start(n.flows[e],n,t)));t.push(s)}return Promise.all(t)}prepare(e){let t=e.pop();const n={};return"string"==typeof t?(e.push(t),t={}):this.dependents(t,n),{flows:e,dependencies:t,dependents:n,execution:{}}}dependents(e,t){for(let[n,s]of Object.entries(e))for(let e=s.length-1;e>=0;e--)t[s[e]]||(t[s[e]]=[]),t[s[e]].push(n)}link_and_start(e,t,n){const s=this.flow[e],o=s.length,i={},r=this.state;for(let c=o-1;c>=0;c--){if("function"!=typeof this.unit[s[c]])return console.log(`Error: Unit "${s[c]}" on flow "${e}" is not a function. This flow execution is stopped.`)&&n();const d=this.unit[s[c]].bind(this),p=c==o-1?n:i[c+1],l=e+":"+s[c],h=async()=>d(r,p,n);i[c]=()=>this.wait_or_run(l,h,t)}i[0]()}wait_or_run(e,t,n,s=!1){if(!s&&!this.dependencies_completed(e,n))return n.execution[e]=()=>this.wait_or_run(e,t,n,!0);n.execution[e]=!0,t(),this.check_dependents(e,n)}dependencies_completed(e,t){const n=t.dependencies[e];return!n||n.every((e=>!0===t.execution[e]))}check_dependents(e,t){const n=t.dependents[e];if(n)for(let e=n.length-1;e>=0;e--){const s=n[e];"function"==typeof t.execution[s]&&(this.dependencies_completed(s,t)&&t.execution[s]())}}}export{e as Unitflow};
diff --git a/package.json b/package.json
index 31d1907..3fea99e 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "@alumna/unitflow",
-	"version": "1.0.2",
+	"version": "1.0.3",
 	"description": "Organize your library or project, defining flows composable by a sequence of units",
 	"exports": {
 		"import": "./dist/unitflow.mjs",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index e44ff4f..2b84600 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -22,7 +22,7 @@ packages:
     engines: {node: '>=6.0.0'}
     dependencies:
       '@jridgewell/gen-mapping': 0.3.3
-      '@jridgewell/trace-mapping': 0.3.21
+      '@jridgewell/trace-mapping': 0.3.22
     dev: true
 
   /@babel/code-frame@7.23.5:
@@ -67,7 +67,7 @@ packages:
     dependencies:
       '@babel/types': 7.23.6
       '@jridgewell/gen-mapping': 0.3.3
-      '@jridgewell/trace-mapping': 0.3.21
+      '@jridgewell/trace-mapping': 0.3.22
       jsesc: 2.5.2
     dev: true
 
@@ -490,7 +490,7 @@ packages:
       '@jest/test-result': 29.7.0
       '@jest/transform': 29.7.0
       '@jest/types': 29.6.3
-      '@jridgewell/trace-mapping': 0.3.21
+      '@jridgewell/trace-mapping': 0.3.22
       '@types/node': 20.11.5
       chalk: 4.1.2
       collect-v8-coverage: 1.0.2
@@ -524,7 +524,7 @@ packages:
     resolution: {integrity: sha512-MHjT95QuipcPrpLM+8JMSzFx6eHp5Bm+4XeFDJlwsvVBjmKNiIAvasGK2fxz2WbGRlnvqehFbh07MMa7n3YJnw==}
     engines: {node: ^14.15.0 || ^16.10.0 || >=18.0.0}
     dependencies:
-      '@jridgewell/trace-mapping': 0.3.21
+      '@jridgewell/trace-mapping': 0.3.22
       callsites: 3.1.0
       graceful-fs: 4.2.11
     dev: true
@@ -555,7 +555,7 @@ packages:
     dependencies:
       '@babel/core': 7.23.7
       '@jest/types': 29.6.3
-      '@jridgewell/trace-mapping': 0.3.21
+      '@jridgewell/trace-mapping': 0.3.22
       babel-plugin-istanbul: 6.1.1
       chalk: 4.1.2
       convert-source-map: 2.0.0
@@ -590,7 +590,7 @@ packages:
     dependencies:
       '@jridgewell/set-array': 1.1.2
       '@jridgewell/sourcemap-codec': 1.4.15
-      '@jridgewell/trace-mapping': 0.3.21
+      '@jridgewell/trace-mapping': 0.3.22
     dev: true
 
   /@jridgewell/resolve-uri@3.1.1:
@@ -607,15 +607,15 @@ packages:
     resolution: {integrity: sha512-UTYAUj/wviwdsMfzoSJspJxbkH5o1snzwX0//0ENX1u/55kkZZkcTZP6u9bwKGkv+dkk9at4m1Cpt0uY80kcpQ==}
     dependencies:
       '@jridgewell/gen-mapping': 0.3.3
-      '@jridgewell/trace-mapping': 0.3.21
+      '@jridgewell/trace-mapping': 0.3.22
     dev: true
 
   /@jridgewell/sourcemap-codec@1.4.15:
     resolution: {integrity: sha512-eF2rxCRulEKXHTRiDrDy6erMYWqNw4LPdQ8UQA4huuxaQsVeRPFl2oM8oDGxMFhJUWZf9McpLtJasDDZb/Bpeg==}
     dev: true
 
-  /@jridgewell/trace-mapping@0.3.21:
-    resolution: {integrity: sha512-SRfKmRe1KvYnxjEMtxEr+J4HIeMX5YBg/qhRHpxEIGjhX1rshcHlnFUE9K0GazhVKWM7B+nARSkV8LuvJdJ5/g==}
+  /@jridgewell/trace-mapping@0.3.22:
+    resolution: {integrity: sha512-Wf963MzWtA2sjrNt+g18IAln9lKnlRp+K2eH4jjIoF1wYeq3aMREpG09xhlhdzS0EjwU7qmUJYangWa+151vZw==}
     dependencies:
       '@jridgewell/resolve-uri': 3.1.1
       '@jridgewell/sourcemap-codec': 1.4.15
@@ -2376,7 +2376,7 @@ packages:
     resolution: {integrity: sha512-/EH/sDgxU2eGxajKdwLCDmQ4FWq+kpi3uCmBGpw1xJtnAxEjlD8j8PEiGWpCIMIs3ciNAgH0d3TTJiUkYzyZjA==}
     engines: {node: '>=10.12.0'}
     dependencies:
-      '@jridgewell/trace-mapping': 0.3.21
+      '@jridgewell/trace-mapping': 0.3.22
       '@types/istanbul-lib-coverage': 2.0.6
       convert-source-map: 2.0.0
     dev: true
diff --git a/src/unitflow.js b/src/unitflow.js
index 66d411d..75bd716 100644
--- a/src/unitflow.js
+++ b/src/unitflow.js
@@ -66,6 +66,10 @@ export class Unitflow {
 
 		for ( let i = length - 1; i >= 0; i-- ) {
 			
+			// ensure it's a function
+			if ( typeof this.unit[ units[i] ] !== 'function' )
+				return console.log( `Error: Unit "${units[i]}" on flow "${flow}" is not a function. This flow execution is stopped.` ) && resolve();
+
 			const 	unit = this.unit[ units[i] ].bind( this ),
 					next = i == ( length - 1 ) ? resolve : sequence[ i + 1 ],
 					name = flow + ':' + units[i],
diff --git a/test/without-dependencies.test.js b/test/without-dependencies.test.js
index aa8ba68..4c2f75c 100644
--- a/test/without-dependencies.test.js
+++ b/test/without-dependencies.test.js
@@ -1,4 +1,5 @@
 import { Unitflow } from './../src/unitflow';
+import { jest } 	from '@jest/globals';
 
 
 describe( 'Flows without dependencies', () => {
@@ -73,4 +74,33 @@ describe( 'Flows without dependencies', () => {
 
 	});
 
+	test('3. Error when an unit isn\'t a function', async () => {
+
+		// console.log mock
+		let log_message;
+		const log = jest.spyOn(console, "log").mockImplementation( message => log_message = message );
+
+		const lib = new Unitflow();
+		
+		expect( lib.state ).toEqual( {} );
+
+		lib.unit[ 'task 1' ] = function ( state, next ) {
+			state[ 'task 1' ] = 'done'
+			next();
+		}
+
+		lib.unit[ 'task 2' ] = 'This string is not a function';
+
+		lib.flow[ 'tasks' ] = [ 'task 1', 'task 2' ]
+
+		await lib.run( 'tasks' )
+
+		expect( lib.state ).toEqual({});
+		expect( log_message ).toBe( 'Error: Unit "task 2" on flow "tasks" is not a function. This flow execution is stopped.' )
+
+		// undo console.log mock
+		log.mockReset();
+
+	});
+
 });
\ No newline at end of file