diff --git a/karma.conf.js b/karma.conf.js
index 37ded8bc..33ea1dde 100644
--- a/karma.conf.js
+++ b/karma.conf.js
@@ -15,6 +15,7 @@ module.exports = function(config) {
             'test/lib/angular-mocks.js',
             'test/helpers.js',
             'test/matchers.js',
+            'src/constants.js',
             'test/*.spec.js',
             'src/init.js',
             'src/*.js',
diff --git a/src/auto-complete.js b/src/auto-complete.js
index 212b1e4c..4927bbeb 100644
--- a/src/auto-complete.js
+++ b/src/auto-complete.js
@@ -219,9 +219,10 @@ tagsInput.directive('autoComplete', function($document, $timeout, $sce, $q, tags
                 })
                 .on('input-keydown', function(event) {
                     var key = event.keyCode,
+                        isModifier = event.shiftKey || event.altKey || event.ctrlKey || event.metaKey,
                         handled = false;
 
-                    if (hotkeys.indexOf(key) === -1) {
+                    if (isModifier || hotkeys.indexOf(key) === -1) {
                         return;
                     }
 
diff --git a/test/auto-complete.spec.js b/test/auto-complete.spec.js
index 1e853f0f..608f7f3a 100644
--- a/test/auto-complete.spec.js
+++ b/test/auto-complete.spec.js
@@ -69,8 +69,8 @@ describe('autoComplete directive', function() {
         $scope.$digest();
     }
 
-    function sendKeyDown(keyCode) {
-        var event = jQuery.Event('keydown', { keyCode: keyCode });
+    function sendKeyDown(keyCode, properties) {
+        var event = jQuery.Event('keydown', angular.extend({ keyCode: keyCode }, properties || {}));
         eventHandlers.call('input-keydown', event);
 
         return event;
@@ -615,157 +615,6 @@ describe('autoComplete directive', function() {
         });
     });
 
-    describe('keys propagation handling', function() {
-        describe('hotkeys - suggestion box is visible', function() {
-            beforeEach(function() {
-                suggestionList.show();
-            });
-
-            it('prevents the down arrow keydown event from being propagated', function() {
-                // Act
-                var event = sendKeyDown(KEYS.down);
-
-                // Assert
-                expect(event.isDefaultPrevented()).toBe(true);
-                expect(event.isPropagationStopped()).toBe(true);
-            });
-
-            it('prevents the up arrow keydown event from being propagated', function() {
-                // Act
-                var event = sendKeyDown(KEYS.up);
-
-                // Assert
-                expect(event.isDefaultPrevented()).toBe(true);
-                expect(event.isPropagationStopped()).toBe(true);
-            });
-
-            it('prevents the enter keydown event from being propagated if there is a suggestion selected', function() {
-                // Arrange
-                suggestionList.selected = 'suggestion';
-
-                // Act
-                var event = sendKeyDown(KEYS.enter);
-
-                // Assert
-                expect(event.isDefaultPrevented()).toBe(true);
-                expect(event.isPropagationStopped()).toBe(true);
-            });
-
-            it('does not prevent the enter keydown event from begin propagated if there is no suggestion selected', function() {
-                // Arrange
-                suggestionList.selected = null;
-
-                // Act
-                var event = sendKeyDown(KEYS.enter);
-
-                // Assert
-                expect(event.isDefaultPrevented()).toBe(false);
-                expect(event.isPropagationStopped()).toBe(false);
-            });
-
-            it('prevents the tab keydown event from being propagated if there is a suggestion selected', function() {
-                // Arrange
-                suggestionList.selected = 'suggestion';
-
-                // Act
-                var event = sendKeyDown(KEYS.tab);
-
-                // Assert
-                expect(event.isDefaultPrevented()).toBe(true);
-                expect(event.isPropagationStopped()).toBe(true);
-            });
-
-            it('does not prevent the tab keydown event from being propagated if there is no suggestion selected', function() {
-                // Arrange
-                suggestionList.selected = null;
-
-                // Act
-                var event = sendKeyDown(KEYS.tab);
-
-                // Assert
-                expect(event.isDefaultPrevented()).toBe(false);
-                expect(event.isPropagationStopped()).toBe(false);
-            });
-
-            it('prevents the escape keydown event from being propagated', function() {
-                // Act
-                var event = sendKeyDown(KEYS.escape);
-
-                // Assert
-                expect(event.isDefaultPrevented()).toBe(true);
-                expect(event.isPropagationStopped()).toBe(true);
-            });
-        });
-
-        describe('hotkeys - suggestion box is hidden', function() {
-            beforeEach(function() {
-                suggestionList.reset();
-            });
-
-            it('does not prevent the down arrow keydown event from being propagated', function() {
-                // Act
-                var event = sendKeyDown(KEYS.down);
-
-                // Assert
-                expect(event.isDefaultPrevented()).toBe(false);
-                expect(event.isPropagationStopped()).toBe(false);
-            });
-
-            it('does not prevent the up arrow keydown event from being propagated', function() {
-                // Act
-                var event = sendKeyDown(KEYS.up);
-
-                // Assert
-                expect(event.isDefaultPrevented()).toBe(false);
-                expect(event.isPropagationStopped()).toBe(false);
-            });
-
-            it('does not prevent the enter keydown event from being propagated', function() {
-                // Act
-                var event = sendKeyDown(KEYS.enter);
-
-                // Assert
-                expect(event.isDefaultPrevented()).toBe(false);
-                expect(event.isPropagationStopped()).toBe(false);
-            });
-
-            it('does not prevent the tab keydown event from being propagated', function() {
-                // Act
-                var event = sendKeyDown(KEYS.tab);
-
-                // Assert
-                expect(event.isDefaultPrevented()).toBe(false);
-                expect(event.isPropagationStopped()).toBe(false);
-            });
-
-            it('does not prevent the escape keydown event from being propagated', function() {
-                // Act
-                var event = sendKeyDown(KEYS.escape);
-
-                // Assert
-                expect(event.isDefaultPrevented()).toBe(false);
-                expect(event.isPropagationStopped()).toBe(false);
-            });
-        });
-
-        describe('non-hotkeys', function() {
-            it('does not prevent non-hotkeys keystrokes from being propagated', function() {
-                // Act
-                var events = [sendKeyDown(65), sendKeyDown(66), sendKeyDown(67)];
-
-                // Assert
-                expect(events[0].isDefaultPrevented()).toBe(false);
-                expect(events[0].isPropagationStopped()).toBe(false);
-
-                expect(events[1].isDefaultPrevented()).toBe(false);
-                expect(events[1].isPropagationStopped()).toBe(false);
-
-                expect(events[2].isDefaultPrevented()).toBe(false);
-                expect(events[2].isPropagationStopped()).toBe(false);
-            });
-        });
-    });
-
     describe('load-on-down-arrow option', function() {
         it('initializes the option to false', function() {
            // Arrange
@@ -1308,4 +1157,149 @@ describe('autoComplete directive', function() {
             expect(scope.$getDisplayText).not.toBeUndefined();
         });
     });
+
+    describe('keys propagation handling', function() {
+        describe('hotkeys', function() {
+            var hotkeys = [KEYS.enter, KEYS.tab, KEYS.escape, KEYS.up, KEYS.down];
+
+            describe('suggestion box is visible', function() {
+                beforeEach(function() {
+                    suggestionList.show();
+                });
+
+                it('prevents the down arrow keydown event from being propagated', function() {
+                    // Act
+                    var event = sendKeyDown(KEYS.down);
+
+                    // Assert
+                    expect(event.isDefaultPrevented()).toBe(true);
+                    expect(event.isPropagationStopped()).toBe(true);
+                });
+
+                it('prevents the up arrow keydown event from being propagated', function() {
+                    // Act
+                    var event = sendKeyDown(KEYS.up);
+
+                    // Assert
+                    expect(event.isDefaultPrevented()).toBe(true);
+                    expect(event.isPropagationStopped()).toBe(true);
+                });
+
+                it('prevents the enter keydown event from being propagated if there is a suggestion selected', function() {
+                    // Arrange
+                    suggestionList.selected = 'suggestion';
+
+                    // Act
+                    var event = sendKeyDown(KEYS.enter);
+
+                    // Assert
+                    expect(event.isDefaultPrevented()).toBe(true);
+                    expect(event.isPropagationStopped()).toBe(true);
+                });
+
+                it('does not prevent the enter keydown event from begin propagated if there is no suggestion selected', function() {
+                    // Arrange
+                    suggestionList.selected = null;
+
+                    // Act
+                    var event = sendKeyDown(KEYS.enter);
+
+                    // Assert
+                    expect(event.isDefaultPrevented()).toBe(false);
+                    expect(event.isPropagationStopped()).toBe(false);
+                });
+
+                it('prevents the tab keydown event from being propagated if there is a suggestion selected', function() {
+                    // Arrange
+                    suggestionList.selected = 'suggestion';
+
+                    // Act
+                    var event = sendKeyDown(KEYS.tab);
+
+                    // Assert
+                    expect(event.isDefaultPrevented()).toBe(true);
+                    expect(event.isPropagationStopped()).toBe(true);
+                });
+
+                it('does not prevent the tab keydown event from being propagated if there is no suggestion selected', function() {
+                    // Arrange
+                    suggestionList.selected = null;
+
+                    // Act
+                    var event = sendKeyDown(KEYS.tab);
+
+                    // Assert
+                    expect(event.isDefaultPrevented()).toBe(false);
+                    expect(event.isPropagationStopped()).toBe(false);
+                });
+
+                it('prevents the escape keydown event from being propagated', function() {
+                    // Act
+                    var event = sendKeyDown(KEYS.escape);
+
+                    // Assert
+                    expect(event.isDefaultPrevented()).toBe(true);
+                    expect(event.isPropagationStopped()).toBe(true);
+                });
+            });
+
+            describe('suggestion box is hidden', function() {
+                beforeEach(function() {
+                    suggestionList.reset();
+                });
+
+                hotkeys.forEach(function(hotkey) {
+                    it('does not prevent the keydown event from being propagated (keycode ' + hotkey + ')', function() {
+                        // Act
+                        var event = sendKeyDown(hotkey);
+
+                        // Assert
+                        expect(event.isDefaultPrevented()).toBe(false);
+                        expect(event.isPropagationStopped()).toBe(false);
+                    });
+                });
+            });
+
+            describe('modifier key is on', function() {
+                beforeEach(function() {
+                    suggestionList.show();
+                });
+
+                hotkeys.forEach(function(hotkey) {
+                    it('does not prevent a hotkey from being propagated when the shift key is down (hotkey ' + hotkey + ')', function() {
+                        expect(sendKeyDown(hotkey, { shiftKey: true }).isDefaultPrevented()).toBe(false);
+                    });
+
+                    it('does not prevent a hotkey from being propagated when the alt key is down (hotkey ' + hotkey + ')', function() {
+                        expect(sendKeyDown(hotkey, { altKey: true }).isDefaultPrevented()).toBe(false);
+                    });
+
+                    it('does not prevent a hotkey from being propagated when the ctrl key is down (hotkey ' + hotkey + ')', function() {
+                        expect(sendKeyDown(hotkey, { ctrlKey: true }).isDefaultPrevented()).toBe(false);
+                    });
+
+                    it('does not prevent a hotkey from being propagated when the meta key is down (hotkey ' + hotkey + ')', function() {
+                        expect(sendKeyDown(hotkey, { metaKey: true }).isDefaultPrevented()).toBe(false);
+                    });
+                });
+            });
+        });
+
+        describe('non-hotkeys', function() {
+            it('does not prevent non-hotkeys keystrokes from being propagated', function() {
+                // Act
+                var events = [sendKeyDown(65), sendKeyDown(66), sendKeyDown(67)];
+
+                // Assert
+                expect(events[0].isDefaultPrevented()).toBe(false);
+                expect(events[0].isPropagationStopped()).toBe(false);
+
+                expect(events[1].isDefaultPrevented()).toBe(false);
+                expect(events[1].isPropagationStopped()).toBe(false);
+
+                expect(events[2].isDefaultPrevented()).toBe(false);
+                expect(events[2].isPropagationStopped()).toBe(false);
+            });
+        });
+    });
 });