diff --git a/docker/reference/regexp-additions.go b/docker/reference/regexp-additions.go
new file mode 100644
index 000000000..7b15871f7
--- /dev/null
+++ b/docker/reference/regexp-additions.go
@@ -0,0 +1,6 @@
+package reference
+
+// Return true if the specified string fully matches `IdentifierRegexp`.
+func IsFullIdentifier(s string) bool {
+	return anchoredIdentifierRegexp.MatchString(s)
+}
diff --git a/docker/reference/regexp_test.go b/docker/reference/regexp_test.go
index 09bc81927..48f721943 100644
--- a/docker/reference/regexp_test.go
+++ b/docker/reference/regexp_test.go
@@ -545,6 +545,9 @@ func TestIdentifierRegexp(t *testing.T) {
 
 	for i := range fullCases {
 		checkRegexp(t, anchoredIdentifierRegexp, fullCases[i])
+		if IsFullIdentifier(fullCases[i].input) != fullCases[i].match {
+			t.Errorf("Expected match for %q to be %v", fullCases[i].input, fullCases[i].match)
+		}
 	}
 
 	for i := range shortCases {