diff --git a/CHANGELOG.md b/CHANGELOG.md
index 56ec0f2..e381a6a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,7 +8,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [unreleased]
 
 ### Changed
-- Clean up mixed Chartist imports
+- Clean up mixed Chartist imports ([#2](https://github.com/stklcode/chartist-plugin-tooltip/pull/2))
+
+### Fixed
+- Fixed support for multiple custom classes as an array ([#3](https://github.com/stklcode/chartist-plugin-tooltip/pull/3))
 
 
 ## [2.0.0] - 18th April 2026
diff --git a/src/scripts/chartist-plugin-tooltip.ts b/src/scripts/chartist-plugin-tooltip.ts
index 16d967e..60fdfa0 100644
--- a/src/scripts/chartist-plugin-tooltip.ts
+++ b/src/scripts/chartist-plugin-tooltip.ts
@@ -106,9 +106,15 @@ export default function ChartistPluginTooltip<T extends BaseChart<any>>(
     }
     if (!tt) {
       tt = document.createElement('div');
-      tt.className = $options.class
-        ? 'chartist-tooltip ' + $options.class
-        : 'chartist-tooltip';
+      tt.classList.add('chartist-tooltip');
+      if ($options.class) {
+        tt.classList.add(
+          ...([] as string[])
+            .concat($options.class)
+            .flatMap(c => c.split(/\s+/))
+            .filter(Boolean)
+        );
+      }
       if ($options.appendToBody) {
         document.body.appendChild(tt);
       } else {
diff --git a/test/chartist-plugin-tooltip.spec.ts b/test/chartist-plugin-tooltip.spec.ts
index 53a7d4a..d1fece7 100644
--- a/test/chartist-plugin-tooltip.spec.ts
+++ b/test/chartist-plugin-tooltip.spec.ts
@@ -39,7 +39,7 @@ describe('Tooltips plugin', () => {
         },
         {
           plugins: [
-            [ChartistPluginTooltip, {class: 'foo', appendToBody: false}]
+            [ChartistPluginTooltip, {class: ['foo', 'bar'], appendToBody: false}]
           ]
         }
       );
@@ -120,7 +120,8 @@ describe('Tooltips plugin', () => {
     assert.equal(getTooltip()!.style.top, '190px');
   });
 
-  it('should set additional class', function () {
+  it('should set additional classes', () => {
     assert.equal(hasClass(getTooltip()!, 'foo'), true);
+    assert.equal(hasClass(getTooltip()!, 'bar'), true);
   });
 });