diff --git a/src/browser/ColorManager.test.ts b/src/browser/ColorManager.test.ts
index 3fbd92f1..019bf42a 100644
--- a/src/browser/ColorManager.test.ts
+++ b/src/browser/ColorManager.test.ts
@@ -320,7 +320,7 @@ describe('ColorManager', () => {
       }
     });
 
-    it('should set one extended ansi colors and keep the other default', () => {
+    it('should set one extended ansi color and keep the other default', () => {
       cm.setTheme({
         extendedAnsi: ['#ffffff']
       });
@@ -328,5 +328,39 @@ describe('ColorManager', () => {
       assert.equal(cm.colors.ansi[16].css, '#ffffff');
       assert.equal(cm.colors.ansi[17].css, DEFAULT_ANSI_COLORS[17].css);
     });
+
+    it('should set extended ansi colors to the default when they are unset', () => {
+      cm.setTheme({
+        extendedAnsi: ['#ffffff']
+      });
+      assert.equal(cm.colors.ansi[16].css, '#ffffff');
+
+      cm.setTheme({
+        extendedAnsi: []
+      });
+      assert.equal(cm.colors.ansi[16].css, DEFAULT_ANSI_COLORS[16].css);
+
+      cm.setTheme({
+        extendedAnsi: ['#ffffff']
+      });
+      assert.equal(cm.colors.ansi[16].css, '#ffffff');
+
+      cm.setTheme({});
+      assert.equal(cm.colors.ansi[16].css, DEFAULT_ANSI_COLORS[16].css);
+    });
+
+    it('should set extended ansi colors to the default when they are partially unset', () => {
+      cm.setTheme({
+        extendedAnsi: ['#ffffff', '#000000']
+      });
+      assert.equal(cm.colors.ansi[16].css, '#ffffff');
+      assert.equal(cm.colors.ansi[17].css, '#000000');
+
+      cm.setTheme({
+        extendedAnsi: ['#ffffff']
+      });
+      assert.equal(cm.colors.ansi[16].css, '#ffffff');
+      assert.equal(cm.colors.ansi[17].css, DEFAULT_ANSI_COLORS[17].css);
+    });
   });
 });
diff --git a/src/browser/ColorManager.ts b/src/browser/ColorManager.ts
index 84e5d58d..9e9891c3 100644
--- a/src/browser/ColorManager.ts
+++ b/src/browser/ColorManager.ts
@@ -151,6 +151,7 @@ export class ColorManager implements IColorManager {
       const opacity = 0.3;
       this.colors.selectionTransparent = color.opacity(this.colors.selectionTransparent, opacity);
     }
+    this.colors.ansi = DEFAULT_ANSI_COLORS.slice();
     this.colors.ansi[0] = this._parseColor(theme.black, DEFAULT_ANSI_COLORS[0]);
     this.colors.ansi[1] = this._parseColor(theme.red, DEFAULT_ANSI_COLORS[1]);
     this.colors.ansi[2] = this._parseColor(theme.green, DEFAULT_ANSI_COLORS[2]);