diff --git a/src/go/go2go/instantiate.go b/src/go/go2go/instantiate.go
index 9cb59ac59e..d21c5fac70 100644
--- a/src/go/go2go/instantiate.go
+++ b/src/go/go2go/instantiate.go
@@ -14,13 +14,15 @@ import (
 // We can look them up either with a types.Object associated with an ast.Ident,
 // or with a types.TypeParam.
 type typeArgs struct {
+	types []types.Type // type arguments in order
 	toAST map[types.Object]ast.Expr
 	toTyp map[*types.TypeParam]types.Type
 }
 
 // newTypeArgs returns a new typeArgs value.
-func newTypeArgs() *typeArgs {
+func newTypeArgs(typeTypes []types.Type) *typeArgs {
 	return &typeArgs{
+		types: typeTypes,
 		toAST: make(map[types.Object]ast.Expr),
 		toTyp: make(map[*types.TypeParam]types.Type),
 	}
@@ -56,7 +58,7 @@ func (t *translator) instantiateFunction(fnident *ast.Ident, astTypes []ast.Expr
 		return nil, err
 	}
 
-	ta := newTypeArgs()
+	ta := newTypeArgs(typeTypes)
 	for i, tf := range decl.Type.TParams.List {
 		for _, tn := range tf.Names {
 			obj, ok := t.info.Defs[tn]
diff --git a/src/go/go2go/rewrite.go b/src/go/go2go/rewrite.go
index bb8448e472..a825e6648d 100644
--- a/src/go/go2go/rewrite.go
+++ b/src/go/go2go/rewrite.go
@@ -41,11 +41,12 @@ func isParameterizedFuncDecl(fd *ast.FuncDecl) bool {
 
 // A translator is used to translate a file from Go with contracts to Go 1.
 type translator struct {
-	info           *types.Info
-	types          map[ast.Expr]types.Type
-	idToFunc       map[types.Object]*ast.FuncDecl
-	instantiations map[*ast.Ident][]*instantiation
-	newDecls       []ast.Decl
+	info               *types.Info
+	types              map[ast.Expr]types.Type
+	idToFunc           map[types.Object]*ast.FuncDecl
+	instantiations     map[*ast.Ident][]*instantiation
+	newDecls           []ast.Decl
+	typeInstantiations map[types.Type][]*typeInstantiation
 }
 
 // An instantiation is a single instantiation of a function.
@@ -54,6 +55,12 @@ type instantiation struct {
 	decl  *ast.Ident
 }
 
+// A typeInstantiation is a single instantiation of a type.
+type typeInstantiation struct {
+	types []types.Type
+	typ   types.Type
+}
+
 // rewrite rewrites the contents of one file.
 func rewriteFile(dir string, fset *token.FileSet, info *types.Info, idToFunc map[types.Object]*ast.FuncDecl, filename string, file *ast.File) (err error) {
 	if err := rewriteAST(info, idToFunc, file); err != nil {
@@ -86,10 +93,11 @@ func rewriteFile(dir string, fset *token.FileSet, info *types.Info, idToFunc map
 // rewriteAST rewrites the AST for a file.
 func rewriteAST(info *types.Info, idToFunc map[types.Object]*ast.FuncDecl, file *ast.File) (err error) {
 	t := translator{
-		info:           info,
-		types:          make(map[ast.Expr]types.Type),
-		idToFunc:       idToFunc,
-		instantiations: make(map[*ast.Ident][]*instantiation),
+		info:               info,
+		types:              make(map[ast.Expr]types.Type),
+		idToFunc:           idToFunc,
+		instantiations:     make(map[*ast.Ident][]*instantiation),
+		typeInstantiations: make(map[types.Type][]*typeInstantiation),
 	}
 	return t.translate(file)
 }
diff --git a/src/go/go2go/types.go b/src/go/go2go/types.go
index 60d4c5f865..3aed203578 100644
--- a/src/go/go2go/types.go
+++ b/src/go/go2go/types.go
@@ -42,6 +42,26 @@ func (t *translator) setType(e ast.Expr, nt types.Type) {
 
 // instantiateType instantiates typ using ta.
 func (t *translator) instantiateType(ta *typeArgs, typ types.Type) types.Type {
+	if insts, ok := t.typeInstantiations[typ]; ok {
+		for _, inst := range insts {
+			if t.sameTypes(ta.types, inst.types) {
+				return inst.typ
+			}
+		}
+	}
+
+	ityp := t.doInstantiateType(ta, typ)
+	typinst := &typeInstantiation{
+		types: ta.types,
+		typ:   ityp,
+	}
+	t.typeInstantiations[typ] = append(t.typeInstantiations[typ], typinst)
+	return ityp
+}
+
+// doInstantiateType does the work of instantiating typ using ta.
+// This should only be called from instantiateType.
+func (t *translator) doInstantiateType(ta *typeArgs, typ types.Type) types.Type {
 	switch typ := typ.(type) {
 	case *types.TypeParam:
 		if instType, ok := ta.typ(typ); ok {