diff --git a/src/go/types/contracts.go b/src/go/types/contracts.go
index e5b656ca73..466daed482 100644
--- a/src/go/types/contracts.go
+++ b/src/go/types/contracts.go
@@ -8,7 +8,6 @@ package types
 
 import (
 	"go/ast"
-	"sort"
 )
 
 // TODO(gri) Handling a contract like a type is problematic because it
@@ -147,28 +146,11 @@ func (check *Checker) contractType(contr *Contract, e *ast.ContractType) {
 	}
 
 	// cleanup/complete interfaces
-	// TODO(gri) should check for duplicate entries in first pass (=> no need for this extra pass)
 	for tpar, iface := range ifaces {
 		if iface == nil {
 			ifaces[tpar] = &emptyInterface
 		} else {
-			var mset objset
-			i := 0
-			for _, m := range iface.methods {
-				if m0 := mset.insert(m); m0 != nil {
-					// A method with the same name exists already.
-					check.errorf(m.Pos(), "method %s already declared", m.name)
-					check.reportAltDecl(m0)
-				} else {
-					// only keep unique methods
-					// TODO(gri) revisit this code - introduced to fix large rebase
-					iface.methods[i] = m
-					i++
-				}
-			}
-			iface.methods = iface.methods[:i]
-			sort.Sort(byUniqueMethodName(iface.methods))
-			iface.Complete()
+			check.completeInterface(iface)
 		}
 	}
 
diff --git a/src/go/types/testdata/contracts.go2 b/src/go/types/testdata/contracts.go2
index 1b6c1c93fc..cd7df220a4 100644
--- a/src/go/types/testdata/contracts.go2
+++ b/src/go/types/testdata/contracts.go2
@@ -19,16 +19,16 @@ type _ contract(A, B, A /* ERROR A redeclared */ ){}
 contract _(A) { A } /* ERROR expected type */
 contract _(A) { A m(); A add(A) int }
 contract _(A) { B /* ERROR B not declared by contract */ m() }
-contract _(A) { A m(); A m /* ERROR already declared */ () }
+contract _(A) { A m(); A m /* ERROR duplicate method */ () }
 contract _(A) {
         A m()
-        A m /* ERROR already declared */ () int
+        A m /* ERROR duplicate method */ () int
 }
 contract _(A, B) {
         A m(x int) B
         B m(x int) A
-        A m /* ERROR already declared */ (x int) B
-        B m /* ERROR already declared */ (x int) B
+        A m /* ERROR duplicate method */ (x int) B
+        B m /* ERROR duplicate method */ (x int) B
 }
 
 contract _(A) {
diff --git a/src/go/types/type.go b/src/go/types/type.go
index bf27599d1b..1a2838a173 100644
--- a/src/go/types/type.go
+++ b/src/go/types/type.go
@@ -371,8 +371,7 @@ func (t *Interface) Complete() *Interface {
 		case other == nil:
 			methods = append(methods, m)
 		case explicit:
-			// TODO(gri) enable again once contracts code calls Complete with correct interfaces
-			// panic("duplicate method " + m.name)
+			panic("duplicate method " + m.name)
 		default:
 			// check method signatures after all locally embedded interfaces are computed
 			todo = append(todo, m, other.(*Func))