diff --git a/plugins/woocommerce-admin/TESTING-INSTRUCTIONS.md b/plugins/woocommerce-admin/TESTING-INSTRUCTIONS.md
index cc9758adf39..32ba48ab1d7 100644
--- a/plugins/woocommerce-admin/TESTING-INSTRUCTIONS.md
+++ b/plugins/woocommerce-admin/TESTING-INSTRUCTIONS.md
@@ -4,6 +4,13 @@
 
 ## 2.1.0
 
+### Correct the Klarna slug #6440
+
+1. Set up a new store with a UK address so that Klarna available as a payment processor
+2. Go to the "Choose payment methods" task item
+3. Set up Klarna. The plugin will install.
+4. Click Continue. It should take you back to the payment methods page - previously it wasn't doing anything but a console error was displayed.
+
 ### Navigation: Reset submenu before making Flyout #6396
 
 -   Download and activate the MailChimp plugin.
diff --git a/plugins/woocommerce-admin/client/task-list/tasks/payments/index.js b/plugins/woocommerce-admin/client/task-list/tasks/payments/index.js
index b3c51c6f405..40962c94560 100644
--- a/plugins/woocommerce-admin/client/task-list/tasks/payments/index.js
+++ b/plugins/woocommerce-admin/client/task-list/tasks/payments/index.js
@@ -99,6 +99,10 @@ class Payments extends Component {
 
 		const method = methods.find( ( option ) => option.key === methodName );
 
+		if ( ! method ) {
+			throw `Method ${ methodName } not found in available methods list`;
+		}
+
 		this.setState( {
 			enabledMethods: {
 				...enabledMethods,
@@ -124,7 +128,15 @@ class Payments extends Component {
 			return;
 		}
 
-		return methods.find( ( method ) => method.key === query.method );
+		const currentMethod = methods.find(
+			( method ) => method.key === query.method
+		);
+
+		if ( ! currentMethod ) {
+			throw `Current method ${ query.method } not found in available methods list`;
+		}
+
+		return currentMethod;
 	}
 
 	getInstallStep() {
@@ -172,6 +184,10 @@ class Payments extends Component {
 		const { enabledMethods } = this.state;
 		const method = methods.find( ( option ) => option.key === key );
 
+		if ( ! method ) {
+			throw `Method ${ key } not found in available methods list`;
+		}
+
 		enabledMethods[ key ] = ! enabledMethods[ key ];
 		this.setState( { enabledMethods } );
 
diff --git a/plugins/woocommerce-admin/client/task-list/tasks/payments/klarna.js b/plugins/woocommerce-admin/client/task-list/tasks/payments/klarna.js
index cc108762fc5..99493e90895 100644
--- a/plugins/woocommerce-admin/client/task-list/tasks/payments/klarna.js
+++ b/plugins/woocommerce-admin/client/task-list/tasks/payments/klarna.js
@@ -18,7 +18,7 @@ class Klarna extends Component {
 		const { markConfigured, plugin } = this.props;
 
 		const slug =
-			plugin === 'checkout' ? 'klarna-checkout' : 'klarna-payments';
+			plugin === 'checkout' ? 'klarna_checkout' : 'klarna_payments';
 
 		markConfigured( slug );
 	}
diff --git a/plugins/woocommerce-admin/readme.txt b/plugins/woocommerce-admin/readme.txt
index 988c0c19d27..0d376bea62c 100644
--- a/plugins/woocommerce-admin/readme.txt
+++ b/plugins/woocommerce-admin/readme.txt
@@ -122,6 +122,7 @@ Release and roadmap notes are available on the [WooCommerce Developers Blog](htt
 - Fix: Reset Navigation submenu before making Flyout #6396
 - Dev: Add a changelog lint check to PRs. #6414
 - Fix: Move the shipping input and text 1px lower. #6408
+- Fix: Correct the Klarna slug #6440
 
 == 2.0.0 02/05/2021 ==