diff --git a/src/RWS.hs b/src/RWS.hs
index adc0b66ea..4d1db49f4 100644
--- a/src/RWS.hs
+++ b/src/RWS.hs
@@ -214,9 +214,9 @@ insertion previous unmappedA unmappedB (UnmappedTerm j _ b) = do
   put (previous, unmappedA, IntMap.delete j unmappedB)
   pure (That j, That b)
 
-genFeaturizedTermsAndDiffs :: (Functor syntax, HasField fields FeatureVector)
-                           => RWSEditScript syntax (Record fields) (Record fields)
-                           -> ([UnmappedTerm syntax (Record fields)], [UnmappedTerm syntax (Record fields)], [MappedDiff syntax (Record fields) (Record fields)], [TermOrIndexOrNone (UnmappedTerm syntax (Record fields))])
+genFeaturizedTermsAndDiffs :: (Functor syntax, HasField fields1 FeatureVector, HasField fields2 FeatureVector)
+                           => RWSEditScript syntax (Record fields1) (Record fields2)
+                           -> ([UnmappedTerm syntax (Record fields1)], [UnmappedTerm syntax (Record fields2)], [MappedDiff syntax (Record fields1) (Record fields2)], [TermOrIndexOrNone (UnmappedTerm syntax (Record fields2))])
 genFeaturizedTermsAndDiffs sesDiffs = let Mapping _ _ a b c d = foldl' combine (Mapping 0 0 [] [] [] []) sesDiffs in (reverse a, reverse b, reverse c, reverse d)
   where combine (Mapping counterA counterB as bs mappedDiffs allDiffs) diff = case diff of
           This term -> Mapping (succ counterA) counterB (featurize counterA term : as) bs mappedDiffs (None : allDiffs)