Index: tests/formatting/EscUrl.php
===================================================================
--- tests/formatting/EscUrl.php	(revision 1041)
+++ tests/formatting/EscUrl.php	(working copy)
@@ -65,4 +65,14 @@
 		$this->assertEquals( 'http://[::127.0.0.1]', esc_url( 'http://[::127.0.0.1]' ) );
 		$this->assertEquals( 'http://[::DEAD:BEEF:DEAD:BEEF:DEAD:BEEF:DEAD:BEEF]', esc_url( 'http://[::DEAD:BEEF:DEAD:BEEF:DEAD:BEEF:DEAD:BEEF]' ) );
 	}
+
+	/**
+	 * @ticket 21974
+	 */
+	function test_colons() {
+		$this->assertEquals( 'http://example.com/?foo=bar:baz', esc_url( 'http://example.com/?foo=bar:baz' ) );
+		$this->assertEquals( 'http://example.com/css?foo=bar:baz', esc_url( 'http://example.com/css?foo=bar:baz' ) );
+		$this->assertEquals( '//example.com/?foo=bar:baz', esc_url( '//example.com/?foo=bar:baz' ) );
+		$this->assertEquals( '//example.com/css?foo=bar:baz', esc_url( '//example.com/css?foo=bar:baz' ) );
+	}
 }