diff --git a/primer/src/Primer/Eval/NormalOrder.hs b/primer/src/Primer/Eval/NormalOrder.hs
index 2666b9765..b3e4583fa 100644
--- a/primer/src/Primer/Eval/NormalOrder.hs
+++ b/primer/src/Primer/Eval/NormalOrder.hs
@@ -44,6 +44,8 @@ import Primer.Core (
     App,
     Case,
     Hole,
+    LAM,
+    Lam,
     Let,
     LetType,
     Letrec
@@ -164,7 +166,7 @@ foldMapExpr extract topDir = flip evalAccumT mempty . go . (topDir,) . focus
           _ ->
             msum $
               (goType =<< focusType' ez)
-                : map (go <=< hoistAccum) (exprChildren dez)
+                : map (go <=< hoistAccum) (exprChildrenClosed dez)
     goType :: TypeZ -> AccumT Cxt f a
     goType tz =
       readerToAccumT (ReaderT $ extract.ty tz)
@@ -313,6 +315,17 @@ exprChildren (d, ez) =
     addBinds ez bs
     pure (d', c)
 
+-- Extract the children of the current focus, except those under an "unknown" binder,
+-- i.e. we extract the body of a let but not the body of a lambda, or the RHS of case branches.
+-- This is used to restrict our evaluation to "closed evaluation".
+-- NB: for consistency we skip all case branches, not just those that bind a variable.
+exprChildrenClosed :: (Dir, ExprZ) -> [Accum Cxt (Dir, ExprZ)]
+exprChildrenClosed (d, ez) = case target ez of
+  Lam{} -> []
+  LAM{} -> []
+  Case{} -> take 1 $ exprChildren (d, ez) -- just the scrutinee
+  _ -> exprChildren (d, ez)
+
 typeChildren :: TypeZ -> [Accum Cxt TypeZ]
 typeChildren tz =
   children' tz <&> \c -> do