diff --git a/Parser/Fix/Simple.hs b/Parser/Fix/Simple.hs
--- a/Parser/Fix/Simple.hs
+++ b/Parser/Fix/Simple.hs
@@ -62,10 +62,12 @@
    case lookup_t t of {
      TokenPlain -> tell [t];
      TokenOper fix1 p1 | or $ map (== fix1) [InfixLeft, InfixRight, InfixNull] ->
-       get >>* span (lookup_t >>>
-                     \ (TokenOper fix2 p2) ->
-                     fix1 == InfixLeft  && p1 <= p2 ||
-                     fix1 == InfixRight && p1 <  p2) >>= tell *=* put . (t:) >>* uncurry mappend
+       get >>* span (lookup_t >>> \ t' ->
+                     case t' of {
+                       TokenOper fix2 p2 -> fix1 == InfixLeft  && p1 <= p2 ||
+                                            fix1 == InfixRight && p1 <  p2;
+                       _                 -> False;
+                     }) >>= tell *=* put . (t:) >>* uncurry mappend
                        | Postfix == fix1 -> tell [t]
                        | Prefix  == fix1 -> modify (t:);
      TokenLParenth -> modify (t:);
diff --git a/fix-parser-simple.cabal b/fix-parser-simple.cabal
--- a/fix-parser-simple.cabal
+++ b/fix-parser-simple.cabal
@@ -1,5 +1,5 @@
 Name:fix-parser-simple
-Version:15319.1
+Version:15320.1
 Description:Simple fix-expression parser
 License:LGPL
 License-File:license.txt