diff --git a/apps/files_external/js/settings.js b/apps/files_external/js/settings.js
index 2f879e1c85..756804238d 100644
--- a/apps/files_external/js/settings.js
+++ b/apps/files_external/js/settings.js
@@ -59,10 +59,24 @@ function highlightBorder($element, highlight) {
 	return highlight;
 }
 
+function isInputValid($input) {
+	var optional = $input.hasClass('optional');
+	switch ($input.attr('type')) {
+		case 'text':
+		case 'password':
+			if ($input.val() === '' && !optional) {
+				return false;
+			}
+			break;
+	}
+	return true;
+}
+
 function highlightInput($input) {
-	if ($input.attr('type') === 'text' || $input.attr('type') === 'password') {
-		return highlightBorder($input,
-			($input.val() === '' && !$input.hasClass('optional')));
+	switch ($input.attr('type')) {
+		case 'text':
+		case 'password':
+			return highlightBorder($input, !isInputValid($input));
 	}
 }
 
@@ -952,7 +966,7 @@ MountConfigListView.prototype = _.extend({
 			if ($input.attr('type') === 'button') {
 				return;
 			}
-			if ($input.val() === '' && !$input.hasClass('optional')) {
+			if (!isInputValid($input)) {
 				missingOptions.push(parameter);
 				return;
 			}
diff --git a/apps/files_external/tests/js/settingsSpec.js b/apps/files_external/tests/js/settingsSpec.js
index b6372649fb..7631dc5a9b 100644
--- a/apps/files_external/tests/js/settingsSpec.js
+++ b/apps/files_external/tests/js/settingsSpec.js
@@ -37,6 +37,7 @@ describe('OCA.External.Settings tests', function() {
 			'<option disable selected>Add storage</option>' +
 			'<option value="\\OC\\TestBackend">Test Backend</option>' +
 			'<option value="\\OC\\AnotherTestBackend">Another Test Backend</option>' +
+			'<option value="\\OC\\InputsTestBackend">Inputs test backend</option>' +
 			'</select>' +
 			'</td>' +
 			'<td class="authentication"></td>' +
@@ -76,6 +77,22 @@ describe('OCA.External.Settings tests', function() {
 						'builtin': true,
 					},
 					'priority': 12
+				},
+				'\\OC\\InputsTestBackend': {
+					'identifier': '\\OC\\InputsTestBackend',
+					'name': 'Inputs test backend',
+					'configuration': {
+						'field_text': 'Text field',
+						'field_password': '*Password field',
+						'field_bool': '!Boolean field',
+						'field_hidden': '#Hidden field',
+						'field_text_optional': '&Text field optional',
+						'field_password_optional': '&*Password field optional'
+					},
+					'authSchemes': {
+						'builtin': true,
+					},
+					'priority': 13
 				}
 			}
 		);
@@ -190,13 +207,70 @@ describe('OCA.External.Settings tests', function() {
 				expect(fakeServer.requests.length).toEqual(1);
 			});
 			// TODO: tests with "applicableUsers" and "applicableGroups"
-			// TODO: test with non-optional config parameters
 			// TODO: test with missing mount point value
 			// TODO: test with personal mounts (no applicable fields)
 			// TODO: test save triggers: paste, keyup, checkbox
 			// TODO: test "custom" field with addScript
 			// TODO: status indicator
 		});
+		describe('validate storage configuration', function() {
+			var $tr;
+
+			beforeEach(function() {
+				$tr = view.$el.find('tr:first');
+				selectBackend('\\OC\\InputsTestBackend');
+			});
+
+			it('lists missing fields in storage errors', function() {
+				var storage = view.getStorageConfig($tr);
+
+				expect(storage.errors).toEqual({
+					backendOptions: ['field_text', 'field_password']
+				});
+			});
+
+			it('highlights missing non-optional fields', function() {
+				_.each([
+					'field_text',
+					'field_password'
+				], function(param) {
+					expect($tr.find('input[data-parameter='+param+']').hasClass('warning-input')).toBe(true);
+				});
+				_.each([
+					'field_bool',
+					'field_hidden',
+					'field_text_optional',
+					'field_password_optional'
+				], function(param) {
+					expect($tr.find('input[data-parameter='+param+']').hasClass('warning-input')).toBe(false);
+				});
+			});
+
+			it('validates correct storage', function() {
+				$tr.find('[name=mountPoint]').val('mountpoint');
+
+				$tr.find('input[data-parameter=field_text]').val('foo');
+				$tr.find('input[data-parameter=field_password]').val('bar');
+				$tr.find('input[data-parameter=field_text_optional]').val('foobar');
+				// don't set field_password_optional
+				$tr.find('input[data-parameter=field_hidden]').val('baz');
+
+				var storage = view.getStorageConfig($tr);
+
+				expect(storage.validate()).toBe(true);
+			});
+
+			it('checks missing mount point', function() {
+				$tr.find('[name=mountPoint]').val('');
+
+				$tr.find('input[data-parameter=field_text]').val('foo');
+				$tr.find('input[data-parameter=field_password]').val('bar');
+
+				var storage = view.getStorageConfig($tr);
+
+				expect(storage.validate()).toBe(false);
+			});
+		});
 		describe('update storage', function() {
 			// TODO
 		});