diff --git a/lib/irc.js b/lib/irc.js
index 991c47d..d6d90c4 100644
--- a/lib/irc.js
+++ b/lib/irc.js
@@ -278,9 +278,11 @@ function isWordBoundary(ch) {
 }
 
 function isURIPrefix(text) {
-	let i = text.search(space);
-	if (i >= 0) {
-		text = text.slice(i);
+	for (let i = text.length - 1; i >= 0; i--) {
+		if (text[i].search(space)) {
+			text = text.slice(i);
+			break;
+		}
 	}
 
 	i = text.indexOf("://");