diff --git a/specs/builder.go b/specs/builder.go
index 37809f97..d50be2fd 100644
--- a/specs/builder.go
+++ b/specs/builder.go
@@ -114,31 +114,33 @@ type MessageSpecBuilder interface {
 type messageSpecBuilder struct{}
 
 type specDummy struct {
-	Name   string          `json:"name,omitempty" xml:"name,omitempty"`
+	Name   string          `json:"name,omitempty"   xml:"name,omitempty"`
 	Fields orderedFieldMap `json:"fields,omitempty" xml:"fields,omitempty"`
 }
 
 type fieldDummy struct {
-	Type        string                 `json:"type,omitempty" xml:"type,omitempty"`
-	Length      int                    `json:"length,omitempty" xml:"length,omitempty"`
-	Description string                 `json:"description,omitempty" xml:"description,omitempty"`
-	Enc         string                 `json:"enc,omitempty" xml:"enc,omitempty"`
-	Prefix      string                 `json:"prefix,omitempty" xml:"prefix,omitempty"`
-	Padding     *paddingDummy          `json:"padding,omitempty" xml:"padding,omitempty"`
-	Tag         *tagDummy              `json:"tag,omitempty" xml:"tag,omitempty"`
-	Subfields   map[string]*fieldDummy `json:"subfields,omitempty" xml:"subfields:omitempty"`
+	Type              string                 `json:"type,omitempty"              xml:"type,omitempty"`
+	Length            int                    `json:"length,omitempty"            xml:"length,omitempty"`
+	Description       string                 `json:"description,omitempty"       xml:"description,omitempty"`
+	Enc               string                 `json:"enc,omitempty"               xml:"enc,omitempty"`
+	Prefix            string                 `json:"prefix,omitempty"            xml:"prefix,omitempty"`
+	Padding           *paddingDummy          `json:"padding,omitempty"           xml:"padding,omitempty"`
+	Tag               *tagDummy              `json:"tag,omitempty"               xml:"tag,omitempty"`
+	Subfields         map[string]*fieldDummy `json:"subfields,omitempty"         xml:"subfields:omitempty"`
+	Bitmap            *fieldDummy            `json:"bitmap,omitempty"            xml:"bitmap,omitempty"`
+	DisableAutoExpand bool                   `json:"disableAutoExpand,omitempty" xml:"disableAutoExpand,omitempty"`
 }
 
 type paddingDummy struct {
 	Type string `json:"type" xml:"type"`
-	Pad  string `json:"pad" xml:"pad"`
+	Pad  string `json:"pad"  xml:"pad"`
 }
 
 type tagDummy struct {
-	Length  int           `json:"length,omitempty" xml:"length,omitempty"`
-	Enc     string        `json:"enc,omitempty" xml:"enc,omitempty"`
+	Length  int           `json:"length,omitempty"  xml:"length,omitempty"`
+	Enc     string        `json:"enc,omitempty"     xml:"enc,omitempty"`
 	Padding *paddingDummy `json:"padding,omitempty" xml:"padding,omitempty"`
-	Sort    string        `json:"sort,omitempty" xml:"sort,omitempty"`
+	Sort    string        `json:"sort,omitempty"    xml:"sort,omitempty"`
 }
 
 func importField(dummyField *fieldDummy, index string) (*field.Spec, error) {
@@ -177,17 +179,30 @@ func importField(dummyField *fieldDummy, index string) (*field.Spec, error) {
 			fieldSpec.Subfields[key] = constructor(subfieldSpec)
 		}
 
-		fieldSpec.Tag = &field.TagSpec{
-			Length: dummyField.Tag.Length,
+		if dummyField.Tag != nil {
+			fieldSpec.Tag = &field.TagSpec{
+				Length: dummyField.Tag.Length,
+			}
+			fieldSpec.Tag.Enc = EncodingsExtToInt[dummyField.Tag.Enc]
+			if dummyField.Tag.Padding != nil {
+				if padderConstructor := PaddersExtToInt[dummyField.Tag.Padding.Type]; padderConstructor != nil {
+					fieldSpec.Tag.Pad = padderConstructor(dummyField.Tag.Padding.Pad)
+				}
+			}
+			fieldSpec.Tag.Sort = SortExtToInt[dummyField.Tag.Sort]
 		}
-		fieldSpec.Tag.Enc = EncodingsExtToInt[dummyField.Tag.Enc]
-		if dummyField.Tag.Padding != nil {
-			if padderConstructor := PaddersExtToInt[dummyField.Tag.Padding.Type]; padderConstructor != nil {
-				fieldSpec.Tag.Pad = padderConstructor(dummyField.Tag.Padding.Pad)
+
+		if dummyField.Bitmap != nil {
+			bitmapSpec, err := importField(dummyField.Bitmap, "field bitmap")
+			if err != nil {
+				return nil, err
 			}
+
+			fieldSpec.Bitmap = field.NewBitmap(bitmapSpec)
 		}
-		fieldSpec.Tag.Sort = SortExtToInt[dummyField.Tag.Sort]
+
 	}
+	fieldSpec.DisableAutoExpand = dummyField.DisableAutoExpand
 	return fieldSpec, nil
 }
 
@@ -218,7 +233,11 @@ func (builder *messageSpecBuilder) ImportJSON(raw []byte) (*iso8583.MessageSpec,
 		}
 		constructor := FieldConstructor[dummyField.Type]
 		if constructor == nil {
-			return nil, fmt.Errorf("no constructor for filed type: %s for field: %d", dummyField.Type, index)
+			return nil, fmt.Errorf(
+				"no constructor for filed type: %s for field: %d",
+				dummyField.Type,
+				index,
+			)
 		}
 		spec.Fields[index] = constructor(fieldSpec)
 	}
@@ -278,7 +297,16 @@ func exportField(internalField field.Field) (*fieldDummy, error) {
 			}
 			dummyField.Tag = tag
 		}
+
+		if spec.Bitmap != nil {
+			bitmap, err := exportField(spec.Bitmap)
+			if err != nil {
+				return nil, err
+			}
+			dummyField.Bitmap = bitmap
+		}
 	}
+	dummyField.DisableAutoExpand = spec.DisableAutoExpand
 
 	return dummyField, nil
 }
@@ -304,7 +332,6 @@ func exportTag(tag *field.TagSpec) (*tagDummy, error) {
 		dummy.Sort = getFunctionName(tag.Sort)
 	}
 	return dummy, nil
-
 }
 
 func exportPad(pad padding.Padder) (*paddingDummy, error) {
@@ -317,6 +344,7 @@ func exportPad(pad padding.Padder) (*paddingDummy, error) {
 	}
 	return nil, fmt.Errorf("unknown padding type: %s", paddingType)
 }
+
 func exportEnc(enc encoding.Encoder) (string, error) {
 	// set encoding
 	encType := reflect.TypeOf(enc).Elem().Name()
diff --git a/specs/builder_test.go b/specs/builder_test.go
index 0a06d207..8af45145 100644
--- a/specs/builder_test.go
+++ b/specs/builder_test.go
@@ -15,7 +15,6 @@ import (
 )
 
 func TestBuilder(t *testing.T) {
-
 	asciiJson, err := Builder.ExportJSON(Spec87ASCII)
 	require.NoError(t, err)
 
@@ -31,7 +30,6 @@ func TestBuilder(t *testing.T) {
 	require.NoError(t, err)
 
 	require.Exactly(t, Spec87Hex.Name, hexSpec.Name)
-
 }
 
 func TestExampleJSONSpec(t *testing.T) {
@@ -87,7 +85,8 @@ func TestSpecWithCompositeFields(t *testing.T) {
 						Pref:        prefix.EBCDIC.Fixed,
 						Pad:         padding.Left('0'),
 					}),
-				}}),
+				},
+			}),
 			30: field.NewNumeric(&field.Spec{
 				Length:      5,
 				Description: "field key that is not next number",
@@ -114,3 +113,138 @@ func TestSpecWithCompositeFields(t *testing.T) {
 
 	require.Exactly(t, testSpec, importedSpec)
 }
+
+func TestSpecWithCompositeBitmapedFields(t *testing.T) {
+	specJSON := []byte(`
+{
+	"name": "TEST Spec",
+	"fields": {
+		"1": {
+			"type": "Composite",
+			"length": 255,
+			"description": "Private use field",
+			"prefix": "ASCII.LL",
+			"bitmap": {
+					"type": "Bitmap",
+					"length": 8,
+					"description": "Bitmap",
+					"enc": "HexToASCII",
+					"prefix": "Hex.Fixed",
+					"disableAutoExpand": true
+			},
+			"subfields": {
+				"1": {
+					"type": "String",
+					"length": 2,
+					"description": "Cardholder certificate Serial Number",
+					"enc": "ASCII",
+					"prefix": "ASCII.Fixed"
+				},
+				"2": {
+					"type": "String",
+					"length": 2,
+					"description": "Merchant certificate Serial Number",
+					"enc": "ASCII",
+					"prefix": "ASCII.Fixed"
+				},
+				"3": {
+					"type": "String",
+					"length": 2,
+					"description": "Transaction ID",
+					"enc": "ASCII",
+					"prefix": "ASCII.Fixed"
+				},
+				"4": {
+					"type": "String",
+					"length": 20,
+					"description": "CAVV",
+					"enc": "ASCII",
+					"prefix": "ASCII.Fixed"
+				},
+				"5": {
+					"type": "String",
+					"length": 20,
+					"description": "CAVV",
+					"enc": "ASCII",
+					"prefix": "ASCII.Fixed"
+				},
+				"6": {
+					"type": "String",
+					"length": 2,
+					"description": "Cardholder certificate Serial Number",
+					"enc": "ASCII",
+					"prefix": "ASCII.Fixed"
+				},
+				"7": {
+					"type": "String",
+					"length": 2,
+					"description": "Merchant certificate Serial Number",
+					"enc": "ASCII",
+					"prefix": "ASCII.Fixed"
+				},
+				"8": {
+					"type": "String",
+					"length": 2,
+					"description": "Transaction ID",
+					"enc": "ASCII",
+					"prefix": "ASCII.Fixed"
+				},
+				"9": {
+					"type": "String",
+					"length": 20,
+					"description": "CAVV",
+					"enc": "ASCII",
+					"prefix": "ASCII.Fixed"
+				},
+				"10": {
+					"type": "String",
+					"length": 6,
+					"description": "CVV2",
+					"enc": "ASCII",
+					"prefix": "ASCII.Fixed"
+				}
+			}
+		}
+	}
+}`)
+
+	spec, err := Builder.ImportJSON(specJSON)
+	require.NoError(t, err)
+
+	data := struct {
+		F1  *field.String
+		F2  *field.String
+		F3  *field.String
+		F4  *field.String
+		F5  *field.String
+		F6  *field.String
+		F7  *field.String
+		F8  *field.String
+		F9  *field.String
+		F10 *field.String
+	}{
+		F10: field.NewStringValue("11 456"),
+	}
+
+	compositeRestored := field.NewComposite(spec.Fields[1].Spec())
+	err = compositeRestored.Marshal(&data)
+	require.NoError(t, err)
+
+	packed, err := compositeRestored.Pack()
+	require.NoError(t, err)
+	require.Equal(t, "22004000000000000011 456", string(packed))
+
+	exportedJSON, err := Builder.ExportJSON(spec)
+	require.NoError(t, err)
+
+	spec, err = Builder.ImportJSON(exportedJSON)
+	require.NoError(t, err)
+
+	compositeRestored = field.NewComposite(spec.Fields[1].Spec())
+	err = compositeRestored.Marshal(&data)
+	require.NoError(t, err)
+
+	packed, err = compositeRestored.Pack()
+	require.NoError(t, err)
+	require.Equal(t, "22004000000000000011 456", string(packed))
+}