diff --git a/src/scroll-timeline-base.js b/src/scroll-timeline-base.js
index 702f346..2c85492 100644
--- a/src/scroll-timeline-base.js
+++ b/src/scroll-timeline-base.js
@@ -457,7 +457,7 @@ export class ScrollTimeline {
   get currentTime() {
     const unresolved = null;
     const container = this.source;
-    if (!container) return unresolved;
+    if (!container || !container.isConnected) return unresolved;
     if (this.phase == 'inactive')
       return unresolved;
     const scrollerStyle = getComputedStyle(container);
diff --git a/test/expected.txt b/test/expected.txt
index c045d1d..2382c52 100644
--- a/test/expected.txt
+++ b/test/expected.txt
@@ -690,7 +690,7 @@ PASS	/scroll-animations/scroll-timelines/constructor.html	'y' is a valid axis va
 PASS	/scroll-animations/scroll-timelines/constructor.html	Creating a ScrollTimeline with an invalid axis value should throw
 PASS	/scroll-animations/scroll-timelines/current-time-nan.html	currentTime should be null for a display: inline source
 PASS	/scroll-animations/scroll-timelines/current-time-nan.html	currentTime should be null for a display: none source
-FAIL	/scroll-animations/scroll-timelines/current-time-nan.html	currentTime should be null for an unattached source
+PASS	/scroll-animations/scroll-timelines/current-time-nan.html	currentTime should be null for an unattached source
 PASS	/scroll-animations/scroll-timelines/current-time-nan.html	currentTime should be null when the source is not a scroller
 PASS	/scroll-animations/scroll-timelines/current-time-root-scroller.html	currentTime calculates the correct time for a document.scrollingElement source
 PASS	/scroll-animations/scroll-timelines/current-time-writing-modes.html	currentTime handles direction: rtl correctly