diff --git a/packages/block-editor/src/components/rich-text/use-paste-handler.js b/packages/block-editor/src/components/rich-text/use-paste-handler.js
index 47800411a0d25..6e5383aabc167 100644
--- a/packages/block-editor/src/components/rich-text/use-paste-handler.js
+++ b/packages/block-editor/src/components/rich-text/use-paste-handler.js
@@ -265,6 +265,9 @@ function removeWindowsFragments( html ) {
 	const startIdx = html.indexOf( startStr );
 	if ( startIdx > -1 ) {
 		html = html.substring( startIdx + startStr.length );
+	} else {
+		// No point looking for EndFragment
+		return html;
 	}
 
 	const endStr = '<!--EndFragment-->';