diff --git a/execution.go b/execution.go
index 3fc7057..6c40a8f 100644
--- a/execution.go
+++ b/execution.go
@@ -756,6 +756,16 @@ func defaultResolver(fname string) Resolver {
 	return func(ctx Context) (interface{}, error) {
 		t := reflect.TypeOf(ctx.Parent())
 		v := reflect.ValueOf(ctx.Parent())
+
+		if t.Kind() == reflect.Ptr {
+			t = t.Elem()
+			v = v.Elem()
+		}
+
+		if t.Kind() != reflect.Struct {
+			return nil, nil
+		}
+
 		for i := 0; i < t.NumField(); i++ {
 			// Get the field, returns https://golang.org/pkg/reflect/#StructField
 			field := t.Field(i)
@@ -930,11 +940,12 @@ func completeValue(ctx *gqlCtx, path []interface{}, ft Type, fs ast.Fields, resu
 
 func getTypes(s *Schema) (map[string]Type, map[string]Directive, map[string][]Type) {
 	types := map[string]Type{
-		"String":  String,
-		"Boolean": Boolean,
-		"Int":     Int,
-		"ID":      ID,
-		"Float":   Float,
+		"String":   String,
+		"Boolean":  Boolean,
+		"Int":      Int,
+		"ID":       ID,
+		"Float":    Float,
+		"DateTime": DateTime,
 	}
 	directives := map[string]Directive{
 		"skip":       skipDirective,
@@ -974,7 +985,7 @@ func typeWalker(types map[string]Type, directives map[string]Directive, implemen
 		return
 	}
 	// TODO: directives are not checked and "walked" through
-	if hf, ok := t.(hasFields); ok {
+	if hf, ok := wt.(hasFields); ok {
 		if o, ok := t.(*Object); ok {
 			for _, i := range o.Implements {
 				if os, ok := implementors[i.Name]; ok {
@@ -987,15 +998,19 @@ func typeWalker(types map[string]Type, directives map[string]Directive, implemen
 			}
 		}
 		for _, f := range hf.GetFields() {
-			for _, arg := range f.GetArguments() {
+			for _, arg := range f.Arguments {
 				typeWalker(types, directives, implementors, arg.Type)
 			}
-			typeWalker(types, directives, implementors, f.GetType())
+			typeWalker(types, directives, implementors, f.Type)
 		}
 	} else if u, ok := wt.(*Union); ok {
-		for _, m := range u.GetMembers() {
+		for _, m := range u.Members {
 			typeWalker(types, directives, implementors, m)
 		}
+	} else if io, ok := wt.(*InputObject); ok {
+		for _, f := range io.Fields {
+			typeWalker(types, directives, implementors, f.Type)
+		}
 	}
 }
 
diff --git a/introspection.go b/introspection.go
index 832f03a..51467a5 100644
--- a/introspection.go
+++ b/introspection.go
@@ -1,5 +1,9 @@
 package gql
 
+import (
+	"encoding/json"
+)
+
 func init() {
 	typeIntrospection.AddField(
 		"interfaces",
@@ -403,12 +407,27 @@ var (
 				Type: String,
 				Resolver: func(ctx Context) (interface{}, error) {
 					if v, ok := ctx.Parent().(*iArgument); ok && v.arg.IsDefaultValueSet() {
-						return v.arg.DefaultValue, nil
-					} else if v, ok := ctx.Parent().(struct {
-						field *InputField
-						name  string
-					}); ok && v.field.IsDefaultValueSet() {
-						return v.field.DefaultValue, nil
+						if unwrapper(v.arg.Type).GetKind() == EnumKind {
+							return v.arg.DefaultValue, nil
+						}
+						if v.arg.DefaultValue != nil {
+							bs, err := json.Marshal(v.arg.DefaultValue)
+							if err != nil {
+								return nil, err
+							}
+							return string(bs), nil
+						}
+					} else if v, ok := ctx.Parent().(iInputField); ok && v.field.IsDefaultValueSet() {
+						if unwrapper(v.field.Type).GetKind() == EnumKind {
+							return v.field.DefaultValue, nil
+						}
+						if v.field.DefaultValue != nil {
+							bs, err := json.Marshal(v.field.DefaultValue)
+							if err != nil {
+								return nil, err
+							}
+							return string(bs), nil
+						}
 					}
 					return nil, nil
 				},