diff --git a/src/Init/System/IOError.lean b/src/Init/System/IOError.lean
index e97905f1d8..9696c4e412 100644
--- a/src/Init/System/IOError.lean
+++ b/src/Init/System/IOError.lean
@@ -59,7 +59,7 @@ IO.Error.userError s
 namespace IO.Error
 
 @[export lean_mk_io_error_eof]
-def mkEofError : IO.Error := unexpectedEof
+def mkEofError : Unit → IO.Error := fun _ => unexpectedEof
 
 @[export lean_mk_io_error_inappropriate_type_file]
 def mkInappropriateTypeFile : String → UInt32 → String → IO.Error :=