diff --git a/cyclonedx.go b/cyclonedx.go
index cca1f62..50d23cf 100644
--- a/cyclonedx.go
+++ b/cyclonedx.go
@@ -19,6 +19,7 @@ package cyclonedx
 
 import (
 	"encoding/xml"
+	"errors"
 	"fmt"
 	"regexp"
 )
@@ -29,6 +30,8 @@ const (
 	BOMFormat = "CycloneDX"
 )
 
+var ErrInvalidSpecVersion = errors.New("invalid specification version")
+
 type Advisory struct {
 	Title string `json:"title,omitempty" xml:"title,omitempty"`
 	URL   string `json:"url" xml:"url"`
diff --git a/cyclonedx_json.go b/cyclonedx_json.go
index 013578f..3d3e71f 100644
--- a/cyclonedx_json.go
+++ b/cyclonedx_json.go
@@ -17,7 +17,9 @@
 
 package cyclonedx
 
-import "encoding/json"
+import (
+	"encoding/json"
+)
 
 func (sv SpecVersion) MarshalJSON() ([]byte, error) {
 	return json.Marshal(sv.String())
@@ -41,6 +43,8 @@ func (sv *SpecVersion) UnmarshalJSON(bytes []byte) error {
 		*sv = SpecVersion1_3
 	case SpecVersion1_4.String():
 		*sv = SpecVersion1_4
+	default:
+		return ErrInvalidSpecVersion
 	}
 
 	return nil
diff --git a/cyclonedx_xml.go b/cyclonedx_xml.go
index 655e1bd..6431094 100644
--- a/cyclonedx_xml.go
+++ b/cyclonedx_xml.go
@@ -183,6 +183,8 @@ func (sv *SpecVersion) UnmarshalXML(d *xml.Decoder, start xml.StartElement) erro
 		*sv = SpecVersion1_3
 	case SpecVersion1_4.String():
 		*sv = SpecVersion1_4
+	default:
+		return ErrInvalidSpecVersion
 	}
 
 	return nil