diff --git a/digest/digest.go b/digest/digest.go
index efbe49bd..2eb5a0cc 100644
--- a/digest/digest.go
+++ b/digest/digest.go
@@ -47,7 +47,7 @@ func NewDigestFromHex(alg, hex string) Digest {
 }
 
 // DigestRegexp matches valid digest types.
-var DigestRegexp = regexp.MustCompile(`[a-zA-Z0-9-_+.]+:[a-zA-Z0-9-_+.=]+`)
+var DigestRegexp = regexp.MustCompile(`[a-zA-Z0-9-_+.]+:[a-fA-F0-9-_+.=]+$`)
 
 var (
 	// ErrDigestInvalidFormat returned when digest format invalid.
@@ -112,6 +112,10 @@ func (d Digest) Validate() error {
 
 	// Continue on for general parser
 
+	if !DigestRegexp.MatchString(s) {
+		return ErrDigestInvalidFormat
+	}
+
 	i := strings.Index(s, ":")
 	if i < 0 {
 		return ErrDigestInvalidFormat