Test for GH-10

mapstructure_bugs_test.go

diff --git a/mapstructure_bugs_test.go b/mapstructure_bugs_test.go
index ddb3b8e..7054f1a 100644
--- a/mapstructure_bugs_test.go
+++ b/mapstructure_bugs_test.go
@@ -23,3 +23,25 @@
 		t.Fatalf("Vother should be nil: %s", result.Vother)
 	}
 }
+
+// GH-10
+func TestDecode_mapInterfaceInterface(t *testing.T) {
+	input := map[interface{}]interface{}{
+		"vfoo":   nil,
+		"vother": nil,
+	}
+
+	var result Map
+	err := Decode(input, &result)
+	if err != nil {
+		t.Fatalf("should not error: %s", err)
+	}
+
+	if result.Vfoo != "" {
+		t.Fatalf("value should be default: %s", result.Vfoo)
+	}
+
+	if result.Vother != nil {
+		t.Fatalf("Vother should be nil: %s", result.Vother)
+	}
+}