diff --git a/accessibility-checker-engine/src/v4/rules/aria_activedescendant_tabindex_valid.ts b/accessibility-checker-engine/src/v4/rules/aria_activedescendant_tabindex_valid.ts
index 62b5e70f2..852ad46aa 100644
--- a/accessibility-checker-engine/src/v4/rules/aria_activedescendant_tabindex_valid.ts
+++ b/accessibility-checker-engine/src/v4/rules/aria_activedescendant_tabindex_valid.ts
@@ -62,8 +62,9 @@ export let aria_activedescendant_tabindex_valid: Rule = {
             return null;
         }
 
-        //check if the attribute 'aria-activedescendant' is valid for the role of the element
-        
+        //ignore if the attribute 'aria-activedescendant' is blank
+        if (ruleContext.getAttribute("aria-activedescendant").trim().length === 0)
+            return;
 
         // If the tabindex attribute is provided then verify that it is 0 or -1
         passed = RPTUtil.isTabbable(ruleContext);
diff --git a/accessibility-checker-engine/test/v2/checker/accessibility/rules/aria_activedescendant_tabindex_valid_ruleunit/activedescendant_blank_tabbable.html b/accessibility-checker-engine/test/v2/checker/accessibility/rules/aria_activedescendant_tabindex_valid_ruleunit/activedescendant_blank_tabbable.html
new file mode 100755
index 000000000..53a980821
--- /dev/null
+++ b/accessibility-checker-engine/test/v2/checker/accessibility/rules/aria_activedescendant_tabindex_valid_ruleunit/activedescendant_blank_tabbable.html
@@ -0,0 +1,41 @@
+<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
+<!--
+   /******************************************************************************
+     Copyright:: 2020- IBM, Inc
+
+    Licensed under the Apache License, Version 2.0 (the "License");
+    you may not use this file except in compliance with the License.
+    You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing, software
+    distributed under the License is distributed on an "AS IS" BASIS,
+    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+    See the License for the specific language governing permissions and
+    limitations under the License.
+  *****************************************************************************/
+-->
+
+<!DOCTYPE html>
+<html lang="en-US">
+  <head>
+    <title>Sandbox</title>
+    <meta charset="UTF-8" />
+  </head>
+
+  <body>
+    <main>
+      <h1>Test page</h1>
+      <input role="combobox" tabindex="-1" aria-activedescendant="" />
+    </main>
+    <script type="text/javascript">
+      UnitTest = {
+          ruleIds: ["aria_activedescendant_tabindex_valid"],
+          results: [
+          
+          ]
+      }
+  </script>
+  </body>
+</html>
\ No newline at end of file
