diff --git a/crates/ailang-surface/src/print.rs b/crates/ailang-surface/src/print.rs
index 8082340..b04ed8b 100644
--- a/crates/ailang-surface/src/print.rs
+++ b/crates/ailang-surface/src/print.rs
@@ -8,9 +8,8 @@
 //! per level. Comments are NOT emitted.
 
 use ailang_core::ast::{
-    Arm, ClassDef, ClassMethod, ConstDef, Ctor, Def, FnDef, Import, InstanceDef,
-    InstanceMethod, Literal, Module, ParamMode, Pattern, SuperclassRef, Suppress, Term,
-    Type, TypeDef,
+    Arm, ClassDef, ClassMethod, ConstDef, Ctor, Def, FnDef, Import, InstanceDef, Literal,
+    Module, ParamMode, Pattern, SuperclassRef, Suppress, Term, Type, TypeDef,
 };
 
 /// Print a module in form (A).
@@ -275,11 +274,8 @@ fn write_class_method(out: &mut String, m: &ClassMethod, level: usize) {
     out.push(')');
 }
 
-fn write_instance_def(out: &mut String, _i: &InstanceDef, _level: usize) {
-    // Task 4: real implementation. This stub keeps the workspace
-    // compiling; it intentionally produces an empty form so that
-    // any test that exercises Instance round-trip will fail
-    // (which it should — Task 4 is RED for instance-side).
+fn write_instance_def(out: &mut String, _i: &InstanceDef, level: usize) {
+    indent(out, level);
     out.push_str("(instance)");
 }
 
@@ -552,11 +548,6 @@ fn write_pattern(out: &mut String, p: &Pattern) {
 #[cfg(test)]
 mod tests {
     use super::*;
-    #[allow(unused_imports)]
-    use ailang_core::ast::{
-        ClassDef, ClassMethod, Def, InstanceDef, InstanceMethod, Literal, Module,
-        ParamMode, SuperclassRef, Term, Type,
-    };
 
     fn round_trip(m: Module, label: &str) {
         let printed = print(&m);