diff --git a/src/pkg/go/ast/filter.go b/src/pkg/go/ast/filter.go
index cf65f4ae65..a9dd080152 100644
--- a/src/pkg/go/ast/filter.go
+++ b/src/pkg/go/ast/filter.go
@@ -4,7 +4,10 @@
 
 package ast
 
-import "go/ast"
+import (
+	"go/ast";
+	"go/token";
+)
 
 
 func filterIdentList(list []*Ident) []*Ident {
@@ -39,21 +42,54 @@ func filterFieldList(list []*Field) []*Field {
 			j++;
 		}
 	}
+	if j > 0 && j < len(list) {
+		// fields have been stripped but there is at least one left;
+		// add a '...' anonymous field instead
+		list[j] = &ast.Field{nil, nil, &ast.Ellipsis{}, nil, nil};
+		j++;
+	}
 	return list[0 : j];
 }
 
 
+func filterParamList(list []*Field) {
+	for _, f := range list {
+		filterType(f.Type);
+	}
+}
+
+
+var noPos token.Position;
+
 func filterType(typ Expr) {
 	switch t := typ.(type) {
 	case *ArrayType:
 		filterType(t.Elt);
 	case *StructType:
-		t.Fields = filterFieldList(t.Fields);
+		// don't change if empty struct
+		if len(t.Fields) > 0 {
+			t.Fields = filterFieldList(t.Fields);
+			if len(t.Fields) == 0 {
+				// all fields have been stripped - make look like forward-decl
+				t.Lbrace = noPos;
+				t.Fields = nil;
+				t.Rbrace = noPos;
+			}
+		}
 	case *FuncType:
-		t.Params = filterFieldList(t.Params);
-		t.Results = filterFieldList(t.Results);
+		filterParamList(t.Params);
+		filterParamList(t.Results);
 	case *InterfaceType:
-		t.Methods = filterFieldList(t.Methods);
+		// don't change if empty interface
+		if len(t.Methods) > 0 {
+			t.Methods = filterFieldList(t.Methods);
+			if len(t.Methods) == 0 {
+				// all methods have been stripped - make look like forward-decl
+				t.Lbrace = noPos;
+				t.Methods = nil;
+				t.Rbrace = noPos;
+			}
+		}
 	case *MapType:
 		filterType(t.Key);
 		filterType(t.Value);