diff --git a/src/ui/styler/FieldStyler.js b/src/ui/styler/FieldStyler.js
index 3d62cd9..07d5ee9 100644
--- a/src/ui/styler/FieldStyler.js
+++ b/src/ui/styler/FieldStyler.js
@@ -1,7 +1,7 @@
 /**
  * Style fields using CSS
  *
- *  Copyright (C) 2016 LoVullo Associates, Inc.
+ *  Copyright (C) 2016, 2017 LoVullo Associates, Inc.
  *
  *  This file is part of liza.
  *
@@ -140,10 +140,11 @@ module.exports = AbstractClass( 'FieldStyler',
         }
         else if ( typeof element.className === 'string' )
         {
-            // note that we use a space instead of a boundary for the character
-            // preceding the match due to the implementation of addClass()
+            // note that the implementation of #addClass adds a space,
+            // but we also need to cater to classes that might have been
+            // added outside of this system
             element.className = element.className.replace(
-                new RegExp( ( ' ' + cls + '\\b' ), 'g' ), ''
+                new RegExp( ( '( +|\\b)' + cls + '\\b' ), 'g' ), ''
             );
         }
 
diff --git a/test/ui/styler/FieldStylerTest.js b/test/ui/styler/FieldStylerTest.js
new file mode 100644
index 0000000..0a4fc09
--- /dev/null
+++ b/test/ui/styler/FieldStylerTest.js
@@ -0,0 +1,98 @@
+/**
+ * Test case for FieldStyler
+ *
+ *  Copyright (C) 2017 LoVullo Associates, Inc.
+ *
+ *  This file is part of the Liza Data Collection Framework
+ *
+ *  Liza is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+const { expect } = require( 'chai' );
+const { Class }  = require( 'easejs' );
+const styler     = require( '../../../' ).ui.styler;
+
+const Sut = styler.FieldStyler.extend(
+{
+    getId() {},
+    isApplied( field, element ) {},
+    applyStyle( field, element, row ) {},
+    revokeStyle( field, element, row ) {},
+    add( element, cls ) { this.addClass( element, cls ); },
+    remove( element, cls ) { this.removeClass( element, cls ); },
+} );
+
+
+describe( 'ui/styler/FieldStyler', () =>
+{
+    [
+        {
+            label:    'adds class using #addClass on empty',
+            given:    '',
+            add:      'foo',
+            expected: ' foo',
+        },
+
+        {
+            label:    'adds class using #addClass with existing',
+            given:    'foo bar',
+            add:      'baz',
+            expected: 'foo bar baz',
+        },
+
+        {
+            label:    'removes class added by #addClass',
+            given:    'cow',
+            add:      'moo',
+            remove:   'moo',
+            expected: 'cow',
+        },
+
+        {
+            label:    'removes class added by #addClass on empty',
+            given:    '',
+            add:      'moo',
+            remove:   'moo',
+            expected: '',
+        },
+
+        {
+            label:    'removes classes added externally',
+            given:    'cow moo',
+            remove:   'cow',
+            expected: ' moo',
+        },
+
+        {
+            label:    'removes duplicate classes',
+            given:    'moo cow cow and',
+            remove:   'cow',
+            expected: 'moo and',
+        },
+    ].forEach( ( { label, given, add, remove, expected } ) =>
+    {
+        it( label, () =>
+        {
+            const element = { className: given };
+            const sut     = Sut();
+
+            // #addClass and #removeClass respectively
+            add && sut.add( element, add )
+            remove && sut.remove( element, remove );
+
+            expect( element.className )
+                .to.equal( expected );
+        } );
+    } );
+} );