diff --git a/src/prolog/heap_print.rs b/src/prolog/heap_print.rs
index b68a580a..606ae539 100644
--- a/src/prolog/heap_print.rs
+++ b/src/prolog/heap_print.rs
@@ -458,9 +458,9 @@ fn non_quoted_token<Iter: Iterator<Item = char>>(mut iter: Iter) -> bool {
         } else if cut_char!(c) {
             iter.next().is_none()
         } else if c == '[' {
-            (iter.next() == Some(']') && iter.next().is_none())
+            iter.next() == Some(']') && iter.next().is_none()
         } else if c == '{' {
-            (iter.next() == Some('}') && iter.next().is_none())
+            iter.next() == Some('}') && iter.next().is_none()
         } else if solo_char!(c) {
             !(c == '(' || c == ')' || c == '}' || c == ']' || c == ',' || c == '%' || c == '|')
         } else {
diff --git a/src/prolog/indexing.rs b/src/prolog/indexing.rs
index 75a47736..c03ff77a 100644
--- a/src/prolog/indexing.rs
+++ b/src/prolog/indexing.rs
@@ -11,13 +11,14 @@ use std::convert::TryFrom;
 use std::hash::Hash;
 use std::rc::Rc;
 
-#[derive(Clone, Copy)]
+#[derive(Debug, Clone, Copy)]
 enum IntIndex {
     External(usize),
     Fail,
     Internal(usize),
 }
 
+#[derive(Debug)]
 pub struct CodeOffsets {
     atom_tbl: TabledData<Atom>,
     pub constants: IndexMap<Constant, ThirdLevelIndex>,
diff --git a/src/prolog/machine/streams.rs b/src/prolog/machine/streams.rs
index 68b2ec3b..6a904aa0 100644
--- a/src/prolog/machine/streams.rs
+++ b/src/prolog/machine/streams.rs
@@ -59,6 +59,7 @@ pub enum EOFAction {
     Reset,
 }
 
+#[derive(Debug)]
 pub enum AtEndOfStream {
     Not,
     End,