diff --git a/src/prolog/heap_print.rs b/src/prolog/heap_print.rs
index e7a6551a..9488d42a 100644
--- a/src/prolog/heap_print.rs
+++ b/src/prolog/heap_print.rs
@@ -56,14 +56,13 @@ pub struct PrinterOutputter {
     contents: String
 }
 
+impl HeapCellValueOutputter for PrinterOutputter {    
+    type Output = String;
 
-impl HeapCellValueOutputter for PrinterOutputter {
     fn new() -> Self {
         PrinterOutputter { contents: String::new() }
     }
 
-    type Output = String;
-
     fn append(&mut self, contents: &str) {
         self.contents += contents;
     }