diff --git a/go.mod b/go.mod
index 6fda630..1baa50b 100644
--- a/go.mod
+++ b/go.mod
@@ -5,7 +5,7 @@ go 1.16
 require (
 	github.com/gin-gonic/gin v1.7.4
 	github.com/labstack/echo/v4 v4.6.1
-	github.com/miketonks/swag v0.0.0-20211006155010-b4fa61e72278 // indirect
+	github.com/miketonks/swag v0.0.0-20211006155010-b4fa61e72278
 	github.com/stretchr/testify v1.7.0
 	github.com/xeipuuv/gojsonschema v1.2.0
 )
diff --git a/swag-validator.go b/swag-validator.go
index ec9f196..084d28e 100644
--- a/swag-validator.go
+++ b/swag-validator.go
@@ -580,6 +580,38 @@ func buildRequestSchema(e *swagger.Endpoint) *RequestSchema {
 	return &r
 }
 
+func convertProperty(p swagger.Property) SchemaProperty {
+	sp := SchemaProperty{
+		Description:          p.Description,
+		Enum:                 p.Enum,
+		Format:               p.Format,
+		Ref:                  p.Ref,
+		Example:              p.Example,
+		Items:                p.Items,
+		Pattern:              p.Pattern,
+		MinItems:             p.MinItems,
+		MaxItems:             p.MaxItems,
+		UniqueItems:          p.UniqueItems,
+		MinLength:            p.MinLength,
+		MaxLength:            p.MaxLength,
+		Minimum:              p.Minimum,
+		Maximum:              p.Maximum,
+		ExclusiveMinimum:     p.ExclusiveMinimum,
+		ExclusiveMaximum:     p.ExclusiveMaximum,
+		AdditionalProperties: p.AdditionalProperties,
+	}
+	if p.Type != "" {
+		sp.Type = strings.Split(p.Type, ",")
+	}
+	if p.Nullable {
+		sp.Type = append(sp.Type, "null")
+	}
+	if prop, ok := p.AdditionalProperties.(*swagger.Property); ok {
+		sp.AdditionalProperties = convertProperty(*prop)
+	}
+	return sp
+}
+
 func buildSchemaDefinitions(api *swagger.API) map[string]SchemaDefinition {
 	defs := map[string]SchemaDefinition{}
 	for _, d := range api.Definitions {
@@ -592,31 +624,7 @@ func buildSchemaDefinitions(api *swagger.API) map[string]SchemaDefinition {
 			AdditionalProperties: d.AdditionalProperties,
 		}
 		for k, p := range d.Properties {
-			sp := SchemaProperty{
-				Description:          p.Description,
-				Enum:                 p.Enum,
-				Format:               p.Format,
-				Ref:                  p.Ref,
-				Example:              p.Example,
-				Items:                p.Items,
-				Pattern:              p.Pattern,
-				MinItems:             p.MinItems,
-				MaxItems:             p.MaxItems,
-				UniqueItems:          p.UniqueItems,
-				MinLength:            p.MinLength,
-				MaxLength:            p.MaxLength,
-				Minimum:              p.Minimum,
-				Maximum:              p.Maximum,
-				ExclusiveMinimum:     p.ExclusiveMinimum,
-				ExclusiveMaximum:     p.ExclusiveMaximum,
-				AdditionalProperties: p.AdditionalProperties,
-			}
-			if p.Type != "" {
-				sp.Type = strings.Split(p.Type, ",")
-			}
-			if p.Nullable {
-				sp.Type = append(sp.Type, "null")
-			}
+			sp := convertProperty(p)
 
 			schemaDef.Properties[k] = sp
 		}
diff --git a/swag-validator_echo_test.go b/swag-validator_echo_test.go
index d4b9b5f..5b97e3c 100644
--- a/swag-validator_echo_test.go
+++ b/swag-validator_echo_test.go
@@ -213,7 +213,7 @@ func TestPayloadEcho(t *testing.T) {
 
 	testTable := []struct {
 		description      string
-		in               payload
+		in               interface{}
 		expectedStatus   int
 		expectedResponse map[string]interface{}
 	}{
@@ -457,6 +457,25 @@ func TestPayloadEcho(t *testing.T) {
 			expectedStatus:   200,
 			expectedResponse: nil,
 		},
+		{
+			description: "Non-nullable map has no null elems, nullable has both null and non-null elems",
+			in: map[string]interface{}{
+				"non_null_elems": map[string]*string{"foo": pString("bar")},
+				"nullable_elems": map[string]*string{"foo": pString("bar"), "baz": nil},
+			},
+			expectedStatus:   200,
+			expectedResponse: nil,
+		},
+		{
+			description: "Non-nullable map has null elems",
+			in: map[string]interface{}{
+				"non_null_elems": map[string]*string{"foo": nil},
+			},
+			expectedStatus: 400,
+			expectedResponse: map[string]interface{}{
+				"non_null_elems.foo": "Invalid type. Expected: string, given: null",
+			},
+		},
 	}
 
 	api := swag.New(swag.Endpoints(endpoint.New("POST", "/validate-test", "Test the validator",
@@ -484,6 +503,10 @@ func TestPayloadEcho(t *testing.T) {
 	}
 }
 
+func pString(s string) *string {
+	return &s
+}
+
 func TestOptionsReturnErrorsEcho(t *testing.T) {
 
 	api := swag.New(
diff --git a/swag-validator_gin_test.go b/swag-validator_gin_test.go
index 891f671..5bb3ec2 100644
--- a/swag-validator_gin_test.go
+++ b/swag-validator_gin_test.go
@@ -220,7 +220,7 @@ func TestPayloadGin(t *testing.T) {
 
 	testTable := []struct {
 		description      string
-		in               payload
+		in               interface{}
 		expectedStatus   int
 		expectedResponse map[string]interface{}
 	}{
@@ -464,6 +464,25 @@ func TestPayloadGin(t *testing.T) {
 			expectedStatus:   200,
 			expectedResponse: nil,
 		},
+		{
+			description: "Non-nullable map has no null elems, nullable has both null and non-null elems",
+			in: map[string]interface{}{
+				"non_null_elems": map[string]*string{"foo": pString("bar")},
+				"nullable_elems": map[string]*string{"foo": pString("bar"), "baz": nil},
+			},
+			expectedStatus:   200,
+			expectedResponse: nil,
+		},
+		{
+			description: "Non-nullable map has null elems",
+			in: map[string]interface{}{
+				"non_null_elems": map[string]*string{"foo": nil},
+			},
+			expectedStatus: 400,
+			expectedResponse: map[string]interface{}{
+				"non_null_elems.foo": "Invalid type. Expected: string, given: null",
+			},
+		},
 	}
 
 	api := swag.New(swag.Endpoints(endpoint.New("POST", "/validate-test", "Test the validator",
diff --git a/swag-validator_test.go b/swag-validator_test.go
index 615b047..61afb85 100644
--- a/swag-validator_test.go
+++ b/swag-validator_test.go
@@ -38,9 +38,12 @@ type payload struct {
 	MaxItemsArr     []string `json:"max_items_arr,omitempty" max_items:"3"`
 	MinItemsArr     []string `json:"min_items_arr,omitempty" min_items:"2"`
 	UniqueItemsAarr []string `json:"unique_items_arr,omitempty" unique_items:"true"`
+
+	NonNullElems  map[string]string  `json:"non_null_elems,omitempty"`
+	NullableElems map[string]*string `json:"nullable_elems,omitempty"`
 }
 
-func preparePostRequest(url string, body payload) *http.Request {
+func preparePostRequest(url string, body interface{}) *http.Request {
 	buff, err := json.Marshal(body)
 	if err != nil {
 		log.Fatalf("Failed to marshal the body: %s", err)