diff --git a/src/Parser.php b/src/Parser.php
index 5bb2248..81175e2 100644
--- a/src/Parser.php
+++ b/src/Parser.php
@@ -91,7 +91,7 @@ public function parse( $string ) {
 				$full = sprintf( '-%s', $full );
 
 				// Remove minus from end of half.
-				$half = \substr( $half, 0, -1 );
+				$half = \substr( (string) $half, 0, -1 );
 			}
 
 			$string = $full . '.' . $half;