diff --git a/src/Lean/Meta/WHNF.lean b/src/Lean/Meta/WHNF.lean
index 86ab6e59f9af..c118459acce2 100644
--- a/src/Lean/Meta/WHNF.lean
+++ b/src/Lean/Meta/WHNF.lean
@@ -625,17 +625,18 @@ where
           | .partialApp   => pure e
           | .stuck _      => pure e
           | .notMatcher   =>
-            matchConstAux f' (fun _ => return e) fun cinfo lvls =>
-              match cinfo with
-              | .recInfo rec    => reduceRec rec lvls e.getAppArgs (fun _ => return e) (fun e => do recordUnfold cinfo.name; go e)
-              | .quotInfo rec   => reduceQuotRec rec e.getAppArgs (fun _ => return e) (fun e => do recordUnfold cinfo.name; go e)
-              | c@(.defnInfo _) => do
-                if (← isAuxDef c.name) then
-                  recordUnfold c.name
-                  deltaBetaDefinition c lvls e.getAppRevArgs (fun _ => return e) go
-                else
-                  return e
-              | _ => return e
+            let .const cname lvls := f' | return e
+            let some cinfo := (← getEnv).find? cname | return e
+            match cinfo with
+            | .recInfo rec    => reduceRec rec lvls e.getAppArgs (fun _ => return e) (fun e => do recordUnfold cinfo.name; go e)
+            | .quotInfo rec   => reduceQuotRec rec e.getAppArgs (fun _ => return e) (fun e => do recordUnfold cinfo.name; go e)
+            | c@(.defnInfo _) => do
+              if (← isAuxDef c.name) then
+                recordUnfold c.name
+                deltaBetaDefinition c lvls e.getAppRevArgs (fun _ => return e) go
+              else
+                return e
+            | _ => return e
       | .proj _ i c =>
         let k (c : Expr) := do
           match (← projectCore? c i) with
@@ -860,7 +861,9 @@ def reduceRecMatcher? (e : Expr) : MetaM (Option Expr) := do
     return none
   else match (← reduceMatcher? e) with
     | .reduced e => return e
-    | _ => matchConstAux e.getAppFn (fun _ => pure none) fun cinfo lvls => do
+    | _ =>
+      let .const cname lvls := e.getAppFn | return none
+      let some cinfo := (← getEnv).find? cname | return none
       match cinfo with
       | .recInfo «rec»  => reduceRec «rec» lvls e.getAppArgs (fun _ => pure none) (fun e => do recordUnfold cinfo.name; pure (some e))
       | .quotInfo «rec» => reduceQuotRec «rec» e.getAppArgs (fun _ => pure none) (fun e => do recordUnfold cinfo.name; pure (some e))