diff --git a/src/Lean/Compiler/LCNF/SpecInfo.lean b/src/Lean/Compiler/LCNF/SpecInfo.lean
index 8c8403d57e..e3786aeb46 100644
--- a/src/Lean/Compiler/LCNF/SpecInfo.lean
+++ b/src/Lean/Compiler/LCNF/SpecInfo.lean
@@ -189,7 +189,11 @@ def saveSpecParamInfo (decls : Array Decl) : CompilerM Unit := do
       let mut paramsInfo := declsInfo[i]!
       let some mask := m.find? decl.name | unreachable!
       trace[Compiler.specialize.info] "{decl.name} {mask}"
-      paramsInfo := Array.zipWith (fun info fixed => if fixed || info matches .user then info else .other) paramsInfo mask
+      paramsInfo := Array.zipWith (as := paramsInfo) (bs := mask) fun info fixed =>
+        if fixed || info matches .user then
+          info
+        else
+          .other
       for j in [:paramsInfo.size] do
         let mut info := paramsInfo[j]!
         if info matches .fixedNeutral && !hasFwdDeps decl paramsInfo j then