diff --git a/go/types/errors.go b/go/types/errors.go
index c95e8936..5eeaa74e 100644
--- a/go/types/errors.go
+++ b/go/types/errors.go
@@ -258,17 +258,19 @@ func writeType(buf *bytes.Buffer, typ Type) {
 
 	case *Struct:
 		buf.WriteString("struct{")
-		for i, f := range t.fields {
-			if i > 0 {
-				buf.WriteString("; ")
-			}
-			if !f.IsAnonymous {
-				buf.WriteString(f.Name)
-				buf.WriteByte(' ')
-			}
-			writeType(buf, f.Type)
-			if tag := t.Tag(i); tag != "" {
-				fmt.Fprintf(buf, " %q", tag)
+		if t.fields != nil {
+			for i, f := range t.fields {
+				if i > 0 {
+					buf.WriteString("; ")
+				}
+				if !f.IsAnonymous {
+					buf.WriteString(f.Name)
+					buf.WriteByte(' ')
+				}
+				writeType(buf, f.Type)
+				if tag := t.Tag(i); tag != "" {
+					fmt.Fprintf(buf, " %q", tag)
+				}
 			}
 		}
 		buf.WriteByte('}')
@@ -289,13 +291,15 @@ func writeType(buf *bytes.Buffer, typ Type) {
 
 	case *Interface:
 		buf.WriteString("interface{")
-		for i, obj := range t.methods.entries {
-			if i > 0 {
-				buf.WriteString("; ")
+		if t.methods != nil {
+			for i, obj := range t.methods.entries {
+				if i > 0 {
+					buf.WriteString("; ")
+				}
+				m := obj.(*Func)
+				buf.WriteString(m.name)
+				writeSignature(buf, m.typ.(*Signature))
 			}
-			m := obj.(*Func)
-			buf.WriteString(m.name)
-			writeSignature(buf, m.typ.(*Signature))
 		}
 		buf.WriteByte('}')
 
diff --git a/go/types/expr.go b/go/types/expr.go
index 1c1708b9..03d01ae3 100644
--- a/go/types/expr.go
+++ b/go/types/expr.go
@@ -152,12 +152,14 @@ func (check *checker) collectMethods(scope *Scope, list *ast.FieldList) *Scope {
 			// embedded interface
 			utyp := typ.Underlying()
 			if ityp, ok := utyp.(*Interface); ok {
-				for _, obj := range ityp.methods.entries {
-					if alt := methods.Insert(obj); alt != nil {
-						check.errorf(list.Pos(), "multiple methods named %s", obj.Name())
-						obj = nil // for callImplicit, below
+				if ityp.methods != nil {
+					for _, obj := range ityp.methods.entries {
+						if alt := methods.Insert(obj); alt != nil {
+							check.errorf(list.Pos(), "multiple methods named %s", obj.Name())
+							obj = nil // for callImplicit, below
+						}
+						check.callImplicitObj(f, obj)
 					}
-					check.callImplicitObj(f, obj)
 				}
 			} else if utyp != Typ[Invalid] {
 				// if utyp is invalid, don't complain (the root cause was reported before)