diff --git a/internal/apis/certmanager/validation/certificate.go b/internal/apis/certmanager/validation/certificate.go
index fb07c64cb..096eeca19 100644
--- a/internal/apis/certmanager/validation/certificate.go
+++ b/internal/apis/certmanager/validation/certificate.go
@@ -131,7 +131,7 @@ func ValidateCertificateSpec(crt *internalcmapi.CertificateSpec, fldPath *field.
 		case internalcmapi.Ed25519KeyAlgorithm:
 			break
 		default:
-			el = append(el, field.Invalid(fldPath.Child("privateKey", "algorithm"), crt.PrivateKey.Algorithm, "must be either empty or one of rsa or ecdsa"))
+			el = append(el, field.Invalid(fldPath.Child("privateKey", "algorithm"), crt.PrivateKey.Algorithm, "must be either empty or one of rsa, ecdsa or ed25519"))
 		}
 	}