diff --git a/src/go/types/testdata/typeparams.go2 b/src/go/types/testdata/typeparams.go2
index b069b24f62..98c5c18927 100644
--- a/src/go/types/testdata/typeparams.go2
+++ b/src/go/types/testdata/typeparams.go2
@@ -37,15 +37,25 @@ func swapswap(type A, B)(a A, b B) (A, B) {
         return swap(B, A)(b, a)
 }
 
-// type F(type A, B) func(A, B) (B, A)
+type F(type A, B) func(A, B) (B, A)
 
-func min(type T)(x, y T) T {
-        //if x < y {
-        //        return x
-        //}
+func min(type T interface{ type int })(x, y T) T {
+        if x < y {
+                return x
+        }
         return y
 }
 
+func _(type T interface{type int, float32})(x, y T) bool { return x < y }
+func _(type T)(x, y T) bool { return x /* ERROR cannot compare */ < y }
+func _(type T interface{type int, float32, bool})(x, y T) bool { return x /* ERROR cannot compare */ < y }
+
+func _(type T C1)(x, y T) bool { return x /* ERROR cannot compare */ < y }
+func _(type T C2)(x, y T) bool { return x < y }
+
+contract C1(T) {}
+contract C2(T) { T int, float32 }
+
 func new(type T)() *T {
         var x T
         return &x
diff --git a/src/go/types/type.go b/src/go/types/type.go
index af56e87892..7536ab716b 100644
--- a/src/go/types/type.go
+++ b/src/go/types/type.go
@@ -259,7 +259,7 @@ func (t *Interface) is(pred func(Type) bool) bool {
 			return false
 		}
 	}
-	return true
+	return len(t.allTypes) > 0 // we must have at least one type! (was bug)
 }
 
 // emptyInterface represents the empty (completed) interface