diff --git a/src/go/types/decl.go b/src/go/types/decl.go
index 022f14484e..7c612ed9b5 100644
--- a/src/go/types/decl.go
+++ b/src/go/types/decl.go
@@ -772,6 +772,11 @@ func (check *Checker) declareTypeParams(tparams []*TypeName, names []*ast.Ident)
 		check.declare(check.scope, name, tpar, check.scope.pos) // TODO(gri) check scope position
 		tparams = append(tparams, tpar)
 	}
+
+	if check.conf.Trace && len(names) > 0 {
+		check.trace(names[0].Pos(), "type params = %v", tparams[len(tparams)-len(names):])
+	}
+
 	return tparams
 }
 
diff --git a/src/go/types/subst.go b/src/go/types/subst.go
index 2a21811b0d..5abfc4d2a9 100644
--- a/src/go/types/subst.go
+++ b/src/go/types/subst.go
@@ -250,7 +250,7 @@ func (subst *subster) typ(typ Type) Type {
 
 			// already instantiated
 			dump(">>> %s already instantiated", t)
-			assert(len(t.targs) == len(t.targs))
+			assert(len(t.targs) == len(t.tparams))
 			// For each (existing) type argument targ, determine if it needs
 			// to be substituted; i.e., if it is or contains a type parameter
 			// that has a type argument for it.
@@ -282,7 +282,9 @@ func (subst *subster) typ(typ Type) Type {
 
 		// TODO(gri) revisit name creation (function local types, etc.) and factor out
 		//           (also, stripArgNames call is an awful hack)
-		name := stripArgNames(TypeString(t, nil)) + "<" + typeListString(new_targs) + ">"
+		var buf bytes.Buffer
+		writeTypeName(&buf, t.obj, nil)
+		name := stripArgNames(buf.String()) + "<" + typeListString(new_targs) + ">"
 		dump(">>> new type name: %s", name)
 		if tname, found := subst.check.typMap[name]; found {
 			dump(">>> instantiated %s found", tname)
diff --git a/src/go/types/typestring.go b/src/go/types/typestring.go
index 3b771a0e27..e6fbacd064 100644
--- a/src/go/types/typestring.go
+++ b/src/go/types/typestring.go
@@ -259,7 +259,10 @@ func writeType(buf *bytes.Buffer, typ Type, qf Qualifier, visited []Type) {
 
 	case *Named:
 		writeTypeName(buf, t.obj, qf)
-		if t.tparams != nil {
+		// Don't write type parameter list again if we have an instantiated type,
+		// recognized by a closing '>'.
+		// TODO(gri) clean up - this is too subtle a hack and too dependent on subst.
+		if buf.Bytes()[buf.Len()-1] != '>' && t.tparams != nil {
 			writeTParamList(buf, t.tparams, qf, visited)
 		}