diff --git a/src/Language/Haskell/Assignment.hs b/src/Language/Haskell/Assignment.hs
index 1922bdb17..cc81846e6 100644
--- a/src/Language/Haskell/Assignment.hs
+++ b/src/Language/Haskell/Assignment.hs
@@ -654,7 +654,7 @@ pattern' :: Assignment
 pattern' = symbol Pattern *> children expressions
 
 patternGuard :: Assignment
-patternGuard = makeTerm <$> symbol PatternGuard <*> children (Syntax.PatternGuard <$> expression <*> expression)
+patternGuard = makeTerm <$> symbol PatternGuard <*> children (Syntax.PatternGuard <$> expression <*> (expression <|> emptyTerm))
 
 pragma :: Assignment
 pragma = makeTerm <$> symbol Pragma <*> (Syntax.Pragma <$> source)