diff --git a/Duper/Fingerprint.lean b/Duper/Fingerprint.lean
index 49929db..0c85f50 100644
--- a/Duper/Fingerprint.lean
+++ b/Duper/Fingerprint.lean
@@ -157,7 +157,7 @@ def transformToUntypedFirstOrderTerm [Monad m] [MonadLiftT MetaM m] (e : Expr) :
      -/
     return .bvar bvarNum
   | Expr.mdata _ e => transformToUntypedFirstOrderTerm e
-  | Expr.letE _ _ _ _ _ => panic! "The letE expression {e} should have been removed by zeta reduction"
+  | Expr.letE _ _ _ _ _ => panic! s!"The letE expression {e} should have been removed by zeta reduction"
   -- Strip away levels
   | Expr.const name _ => return Expr.const name []
   | _ => return e -- Expr.fvar, Expr.mvar, Expr.lit, Expr.const, and Expr.sort cases
diff --git a/Duper/Util/Reduction.lean b/Duper/Util/Reduction.lean
index 4f22b3a..8038bd2 100644
--- a/Duper/Util/Reduction.lean
+++ b/Duper/Util/Reduction.lean
@@ -44,11 +44,12 @@ partial def preprocessFact (fact : Expr) : MetaM Expr := do
     -- Restore ≠, i.e., ¬ a = b ⇒ a ≠ b
     -- If we don't do this, it seems that clausification will become more inefficient
     let fact ← Core.transform fact (pre := restoreNE)
+    let fact ← zetaReduce fact
     trace[duper.preprocessing.debug] "fact after preprocessing: {fact}"
     return fact
   else
-    trace[duper.preprocessing.debug] "Skipping preprocessing because reduceInstances option is set to false"
-    return fact
+    trace[duper.preprocessing.debug] "reduceInstances option is set to false, only applying zeta reduction"
+    zetaReduce fact
 
 /-- Eta-expand a beta-reduced expression. This function is currently unused -/
 partial def etaLong (e : Expr) : MetaM Expr := do
@@ -101,13 +102,13 @@ partial def etaReduce (e : Expr) : MetaM Expr := do
     | none => return .done e
   Meta.transform e (post := post) (usedLetOnly := true)
 
-/-- Instantiates mvars then applies beta, eta and zeta reduction exhaustively. -/
+/-- Instantiates mvars then applies beta and eta reduction exhaustively. -/
 def betaEtaReduceInstMVars (e : Expr) : MetaM Expr := do
   let e ← instantiateMVars e
   let e ← Core.betaReduce e
   etaReduce e
 
-/-- Applies beta, eta and zeta reduction exhaustively -/
+/-- Applies beta and eta reduction exhaustively -/
 def betaEtaReduce (e : Expr) : MetaM Expr := do
   let e ← Core.betaReduce e
   etaReduce e