diff --git a/packages/app-staking/src/Account/Bond.tsx b/packages/app-staking/src/Account/Bond.tsx
index ce5912277f..1c2a95f89a 100644
--- a/packages/app-staking/src/Account/Bond.tsx
+++ b/packages/app-staking/src/Account/Bond.tsx
@@ -6,7 +6,6 @@ import { I18nProps } from '@polkadot/ui-app/types';
 
 import BN from 'bn.js';
 import React from 'react';
-import { AccountId } from '@polkadot/types';
 import { Button, InputAddress, InputBalance, Modal, TxButton, Dropdown } from '@polkadot/ui-app';
 
 import translate from '../translate';
@@ -14,7 +13,7 @@ import ValidateController from './ValidateController';
 
 type Props = I18nProps & {
   accountId: string,
-  controllerId?: AccountId | null,
+  controllerId?: string | null,
   isOpen: boolean,
   onClose: () => void
 };
diff --git a/packages/app-staking/src/Account/Nominating.tsx b/packages/app-staking/src/Account/Nominating.tsx
index 0fd2fef4cf..2a70f20a31 100644
--- a/packages/app-staking/src/Account/Nominating.tsx
+++ b/packages/app-staking/src/Account/Nominating.tsx
@@ -6,7 +6,6 @@ import { I18nProps } from '@polkadot/ui-app/types';
 import { KeyringSectionOption } from '@polkadot/ui-keyring/options/types';
 
 import React from 'react';
-import { AccountId } from '@polkadot/types';
 import { Button, InputAddress, Modal, TxButton } from '@polkadot/ui-app';
 
 import translate from '../translate';
@@ -15,7 +14,7 @@ type Props = I18nProps & {
   accountId: string,
   isOpen: boolean,
   onClose: () => void,
-  stashId: AccountId,
+  stashId: string,
   stashOptions: Array<KeyringSectionOption>
 };
 
diff --git a/packages/app-staking/src/Account/SessionKey.tsx b/packages/app-staking/src/Account/SessionKey.tsx
index 5328fad699..37751f319c 100644
--- a/packages/app-staking/src/Account/SessionKey.tsx
+++ b/packages/app-staking/src/Account/SessionKey.tsx
@@ -7,15 +7,18 @@ import { I18nProps } from '@polkadot/ui-app/types';
 import React from 'react';
 import { Button, InputAddress, Modal, TxButton } from '@polkadot/ui-app';
 
+import ValidateSession from './ValidateSession';
 import translate from '../translate';
 
 type Props = I18nProps & {
   accountId: string,
   isOpen: boolean,
-  onClose: () => void
+  onClose: () => void,
+  stashId: string
 };
 
 type State = {
+  sessionError: string | null,
   sessionId: string
 };
 
@@ -26,13 +29,14 @@ class Key extends React.PureComponent<Props, State> {
     super(props);
 
     this.state = {
+      sessionError: null,
       sessionId: props.accountId
     };
   }
 
   render () {
     const { accountId, isOpen, onClose, t } = this.props;
-    const { sessionId } = this.state;
+    const { sessionError, sessionId } = this.state;
 
     if (!isOpen) {
       return null;
@@ -56,7 +60,7 @@ class Key extends React.PureComponent<Props, State> {
           <Button.Or />
           <TxButton
             accountId={accountId}
-            isDisabled={!sessionId}
+            isDisabled={!sessionId || !!sessionError}
             isPrimary
             label={t('Set Session Key')}
             onClick={onClose}
@@ -70,7 +74,7 @@ class Key extends React.PureComponent<Props, State> {
   }
 
   private renderContent () {
-    const { accountId, t } = this.props;
+    const { accountId, stashId, t } = this.props;
     const { sessionId } = this.state;
 
     return (
@@ -93,6 +97,12 @@ class Key extends React.PureComponent<Props, State> {
             value={sessionId}
             type='account'
           />
+          <ValidateSession
+            controllerId={accountId}
+            onError={this.onSessionError}
+            sessionId={sessionId}
+            stashId={stashId}
+          />
         </Modal.Content>
       </>
     );
@@ -101,6 +111,10 @@ class Key extends React.PureComponent<Props, State> {
   private onChangeSession = (sessionId: string) => {
     this.setState({ sessionId });
   }
+
+  private onSessionError = (sessionError: string | null) => {
+    this.setState({ sessionError });
+  }
 }
 
 export default translate(Key);
diff --git a/packages/app-staking/src/Account/Unbond.tsx b/packages/app-staking/src/Account/Unbond.tsx
index 2968ac3b68..8ebf579970 100644
--- a/packages/app-staking/src/Account/Unbond.tsx
+++ b/packages/app-staking/src/Account/Unbond.tsx
@@ -2,7 +2,6 @@
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
 
-import { AccountId } from '@polkadot/types';
 import BN from 'bn.js';
 import { Button, InputAddress, InputBalance, Modal, TxButton } from '@polkadot/ui-app';
 import { I18nProps } from '@polkadot/ui-app/types';
@@ -11,7 +10,7 @@ import React from 'react';
 import translate from '../translate';
 
 type Props = I18nProps & {
-  controllerId?: AccountId | null,
+  controllerId?: string | null,
   isOpen: boolean,
   onClose: () => void
 };
@@ -49,7 +48,7 @@ class Unbond extends React.PureComponent<Props, State> {
             />
             <Button.Or />
             <TxButton
-              accountId={controllerId && controllerId.toString()}
+              accountId={controllerId}
               isDisabled={!canSubmit}
               isPrimary
               label={t('Unbond')}
@@ -74,7 +73,7 @@ class Unbond extends React.PureComponent<Props, State> {
         <Modal.Content className='ui--signer-Signer-Content'>
           <InputAddress
             className='medium'
-            defaultValue={controllerId && controllerId.toString()}
+            defaultValue={controllerId}
             isDisabled
             label={t('controler account')}
           />
diff --git a/packages/app-staking/src/Account/ValidateSession.tsx b/packages/app-staking/src/Account/ValidateSession.tsx
new file mode 100644
index 0000000000..64a9183ce9
--- /dev/null
+++ b/packages/app-staking/src/Account/ValidateSession.tsx
@@ -0,0 +1,71 @@
+// Copyright 2017-2019 @polkadot/ui-staking authors & contributors
+// This software may be modified and distributed under the terms
+// of the Apache-2.0 license. See the LICENSE file for details.
+
+import { I18nProps } from '@polkadot/ui-app/types';
+
+import React from 'react';
+import { Icon } from '@polkadot/ui-app';
+import keyring from '@polkadot/ui-keyring';
+
+import translate from '../translate';
+
+type Props = I18nProps & {
+  controllerId: string,
+  onError: (error: string | null) => void,
+  sessionId: string,
+  stashId: string
+};
+
+type State = {
+  error: string | null
+};
+
+class ValidateSession extends React.PureComponent<Props, State> {
+  state: State = {
+    error: null
+  };
+
+  static getDerivedStateFromProps ({ onError, sessionId, stashId, t }: Props, prevState: State): State | null {
+    let error = null;
+
+    try {
+      const pair = keyring.getPair(sessionId);
+
+      if (pair.type !== 'ed25519') {
+        error = t('The selected account is not an ed25519 (Edwards) account as required for validation');
+      } else if (sessionId === stashId) {
+        error = t('For fund security, your session key should not match your stash key.');
+      } else {
+        error = null;
+      }
+    } catch (e) {
+      // this _should_ never happen...
+      error = t('The account {{sessionId}} is not a valid account', { replace: { sessionId } });
+    }
+
+    if (error === prevState.error) {
+      return null;
+    }
+
+    onError(error);
+
+    return { error };
+  }
+
+  render () {
+    const { error } = this.state;
+
+    if (!error) {
+      return null;
+    }
+
+    return (
+      <article className='warning'>
+        <div><Icon name='warning sign' />{error}</div>
+      </article>
+    );
+  }
+}
+
+export default translate(ValidateSession);
diff --git a/packages/app-staking/src/Account/Validating.tsx b/packages/app-staking/src/Account/Validating.tsx
index 769d22e193..8d29ea5615 100644
--- a/packages/app-staking/src/Account/Validating.tsx
+++ b/packages/app-staking/src/Account/Validating.tsx
@@ -6,7 +6,7 @@ import { I18nProps } from '@polkadot/ui-app/types';
 
 import BN from 'bn.js';
 import React from 'react';
-import { AccountId, ValidatorPrefs } from '@polkadot/types';
+import { ValidatorPrefs } from '@polkadot/types';
 import { Button, InputAddress, InputBalance, InputNumber, Modal, TxButton } from '@polkadot/ui-app';
 
 import translate from '../translate';
@@ -16,7 +16,7 @@ type Props = I18nProps & {
   isOpen: boolean,
   onClose: () => void,
   preferences: ValidatorPrefs,
-  stashId: AccountId
+  stashId: string
 };
 
 type State = {
diff --git a/packages/app-staking/src/Account/index.tsx b/packages/app-staking/src/Account/index.tsx
index 0df8b44ba0..c42abf9659 100644
--- a/packages/app-staking/src/Account/index.tsx
+++ b/packages/app-staking/src/Account/index.tsx
@@ -23,13 +23,13 @@ import Validating from './Validating';
 type Props = ApiProps & I18nProps & {
   accountId: string,
   balances: DerivedBalancesMap,
-  controllerId?: AccountId | null,
+  controllerId?: string | null,
   filter: AccountFilter,
   isValidator: boolean,
   name: string,
   recentlyOffline: RecentlyOfflineMap,
-  sessionId?: AccountId | null,
-  stashId?: AccountId | null,
+  sessionId?: string | null,
+  stashId?: string | null,
   freeBalance?: Balance,
   staking_stakers?: Exposure,
   staking_nominators?: [Array<AccountId>],
@@ -132,11 +132,11 @@ class Account extends React.PureComponent<Props, State> {
     const { isUnbondOpen } = this.state;
 
     return (
-        <Unbond
-          controllerId={controllerId}
-          isOpen={isUnbondOpen}
-          onClose={this.toggleUnbond}
-        />
+      <Unbond
+        controllerId={controllerId}
+        isOpen={isUnbondOpen}
+        onClose={this.toggleUnbond}
+      />
     );
   }
 
@@ -160,14 +160,19 @@ class Account extends React.PureComponent<Props, State> {
   }
 
   private renderSessionKey () {
-    const { accountId } = this.props;
+    const { accountId, stashId } = this.props;
     const { isSessionKeyOpen } = this.state;
 
+    if (!stashId) {
+      return null;
+    }
+
     return (
       <SessionKey
         accountId={accountId}
         isOpen={isSessionKeyOpen}
         onClose={this.toggleSessionKey}
+        stashId={stashId}
       />
     );
   }
@@ -209,7 +214,7 @@ class Account extends React.PureComponent<Props, State> {
         <label className='staking--label'>{t('controller')}</label>
         <AddressMini
           value={controllerId}
-          offlineStatus={recentlyOffline[controllerId.toString()]}
+          offlineStatus={recentlyOffline[controllerId]}
         />
       </div>
     );
@@ -242,7 +247,7 @@ class Account extends React.PureComponent<Props, State> {
         <label className='staking--label'>{t('stash')}</label>
         <AddressMini
           value={stashId}
-          offlineStatus={recentlyOffline[stashId.toString()]}
+          offlineStatus={recentlyOffline[stashId]}
           withBalance={false}
           withBonded
         />
@@ -404,6 +409,12 @@ class Account extends React.PureComponent<Props, State> {
   }
 }
 
+function toIdString (id: AccountId | null): string | null {
+  return id
+    ? id.toString()
+    : null;
+}
+
 export default translate(
   withCalls<Props>(
     'query.staking.recentlyOffline',
@@ -411,19 +422,19 @@ export default translate(
       paramName: 'accountId',
       propName: 'sessionId',
       transform: (session: Option<AccountId>) =>
-        session.unwrapOr(null)
+        toIdString(session.unwrapOr(null))
     }],
     ['query.staking.bonded', {
       paramName: 'accountId',
       propName: 'controllerId',
       transform: (bonded: Option<AccountId>) =>
-        bonded.unwrapOr(null)
+        toIdString(bonded.unwrapOr(null))
     }],
     ['query.staking.ledger', {
       paramName: 'accountId',
       propName: 'stashId',
       transform: (ledger: Option<StakingLedger>) =>
-        ledger.unwrapOr({ stash: null }).stash
+        toIdString(ledger.unwrapOr({ stash: null }).stash)
     }],
     ['query.staking.ledger', {
       paramName: 'controllerId',