diff --git a/foliage b/foliage
index 9076ecd..8870cee 160000
--- a/foliage
+++ b/foliage
@@ -1 +1 @@
-Subproject commit 9076ecd95ddd0e0244a8d3782d43b4708f0f05b0
+Subproject commit 8870cee1793571a313ac4f0948e4d73c5589e671
diff --git a/src/format_tptp.rs b/src/format_tptp.rs
index b2de09d..a6e1cc2 100644
--- a/src/format_tptp.rs
+++ b/src/format_tptp.rs
@@ -62,7 +62,7 @@ fn collect_predicate_declarations_in_formula<'a>(
 			{
 				collect_predicate_declarations_in_formula(predicate_declarations, argument);
 			},
-		foliage::Formula::Implies(ref left, ref right) =>
+		foliage::Formula::Implies(ref left, ref right, _) =>
 		{
 			collect_predicate_declarations_in_formula(predicate_declarations, left);
 			collect_predicate_declarations_in_formula(predicate_declarations, right);
@@ -162,7 +162,7 @@ fn collect_symbolic_constants_in_formula<'a>(
 			{
 				collect_symbolic_constants_in_formula(symbolic_constants, argument);
 			},
-		foliage::Formula::Implies(ref left, ref right) =>
+		foliage::Formula::Implies(ref left, ref right, _) =>
 		{
 			collect_symbolic_constants_in_formula(symbolic_constants, left);
 			collect_symbolic_constants_in_formula(symbolic_constants, right);
@@ -515,7 +515,11 @@ impl<'a> std::fmt::Debug for FormulaDisplay<'a>
 
 				write!(format, ")")
 			},
-			foliage::Formula::Implies(ref left, ref right) => write!(format, "({:?} => {:?})", left.display_tptp(), right.display_tptp()),
+			foliage::Formula::Implies(ref left, ref right, implication_direction) => match implication_direction
+			{
+				foliage::ImplicationDirection::LeftToRight => write!(format, "({:?} => {:?})", left.display_tptp(), right.display_tptp()),
+				foliage::ImplicationDirection::RightToLeft => write!(format, "({:?} <= {:?})", left.display_tptp(), right.display_tptp()),
+			},
 			foliage::Formula::Biconditional(ref left, ref right) => write!(format, "({:?} <=> {:?})", left.display_tptp(), right.display_tptp()),
 			foliage::Formula::Less(ref left, ref right) => display_comparison(Notation::Prefix, "$less", Some("p__less__"), left, right),
 			foliage::Formula::LessOrEqual(ref left, ref right) => display_comparison(Notation::Prefix, "$lesseq", Some("p__less_equal__"), left, right),