diff --git a/packages/core/src/browser/style/tabs.css b/packages/core/src/browser/style/tabs.css
index 2d94ce03e271e..699e8efb3be8c 100644
--- a/packages/core/src/browser/style/tabs.css
+++ b/packages/core/src/browser/style/tabs.css
@@ -335,6 +335,7 @@ body.theia-editor-highlightModifiedTabs
 .p-TabBar-content-container {
   display: flex;
   flex: 1;
+  position: relative; /* This is necessary for perfect-scrollbar */
 }
 
 .p-TabBar-toolbar .item {