diff --git a/js/src/modals/ExecuteContract/executeContract.js b/js/src/modals/ExecuteContract/executeContract.js
index 67f350feb..e0462982d 100644
--- a/js/src/modals/ExecuteContract/executeContract.js
+++ b/js/src/modals/ExecuteContract/executeContract.js
@@ -19,7 +19,7 @@ import ActionDoneAll from 'material-ui/svg-icons/action/done-all';
 import ContentClear from 'material-ui/svg-icons/content/clear';
 
 import { BusyStep, CompletedStep, Button, IdentityIcon, Modal, TxHash } from '../../ui';
-import { validateAddress } from '../../util/validation';
+import { validateAddress, validateUint } from '../../util/validation';
 
 import DetailsStep from './DetailsStep';
 
@@ -41,6 +41,7 @@ export default class ExecuteContract extends Component {
   state = {
     amount: '0',
     amountError: null,
+    fromAddressError: null,
     func: null,
     funcError: null,
     values: [],
@@ -77,7 +78,8 @@ export default class ExecuteContract extends Component {
 
   renderDialogActions () {
     const { onClose, fromAddress } = this.props;
-    const { sending, step } = this.state;
+    const { sending, step, fromAddressError, valuesError } = this.state;
+    const hasError = fromAddressError || valuesError.find((error) => error);
     const cancelBtn = (
       <Button
         key='cancel'
@@ -92,7 +94,7 @@ export default class ExecuteContract extends Component {
         <Button
           key='postTransaction'
           label='post transaction'
-          disabled={ sending }
+          disabled={ sending || hasError }
           icon={ <IdentityIcon address={ fromAddress } button /> }
           onClick={ this.postTransaction } />
       ];
@@ -177,12 +179,16 @@ export default class ExecuteContract extends Component {
     let valueError = null;
 
     switch (input.kind.type) {
+      case 'address':
+        valueError = validateAddress(_value).addressError;
+        break;
+
       case 'bool':
         value = _value === 'true';
         break;
 
-      case 'address':
-        valueError = validateAddress(_value).addressError;
+      case 'uint':
+        valueError = validateUint(_value).valueError;
         break;
     }
 
@@ -190,8 +196,8 @@ export default class ExecuteContract extends Component {
     valuesError[index] = valueError;
 
     this.setState({
-      values,
-      valuesError
+      values: [].concat(values),
+      valuesError: [].concat(valuesError)
     });
   }
 
diff --git a/js/src/util/validation.js b/js/src/util/validation.js
index 243217077..dd6e22911 100644
--- a/js/src/util/validation.js
+++ b/js/src/util/validation.js
@@ -14,6 +14,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
+import BigNumber from 'bignumber.js';
+
 import util from '../api/util';
 
 export const ERRORS = {
@@ -22,7 +24,10 @@ export const ERRORS = {
   invalidChecksum: 'address has failed the checksum formatting',
   invalidName: 'name should not be blank and longer than 2',
   invalidAbi: 'abi should be a valid JSON array',
-  invalidCode: 'code should be the compiled hex string'
+  invalidCode: 'code should be the compiled hex string',
+  invalidNumber: 'invalid number format',
+  negativeNumber: 'input number should be positive',
+  decimalNumber: 'input number should not contain decimals'
 };
 
 export function validateAbi (abi, api) {
@@ -88,3 +93,23 @@ export function validateName (name) {
     nameError
   };
 }
+
+export function validateUint (value) {
+  let valueError = null;
+
+  try {
+    const bn = new BigNumber(value);
+    if (bn.lt(0)) {
+      valueError = ERRORS.negativeNumber;
+    } else if (bn.toString().indexOf('.') !== -1) {
+      valueError = ERRORS.decimalNumber;
+    }
+  } catch (e) {
+    valueError = ERRORS.invalidNumber;
+  }
+
+  return {
+    value,
+    valueError
+  };
+}