diff --git a/src/description.cpp b/src/description.cpp
index e89fe1237..bd4cd6350 100644
--- a/src/description.cpp
+++ b/src/description.cpp
@@ -1330,9 +1330,8 @@ std::string CertificateFingerprint::AlgorithmIdentifier(
 }
 
 bool CertificateFingerprint::isValid() const {
-	auto expectedSize = AlgorithmSize(algorithm);
-
-	if (this->value.size() != expectedSize * 3 - 1) {
+	size_t expectedSize = AlgorithmSize(this->algorithm);
+	if (expectedSize == 0 || this->value.size() != expectedSize * 3 - 1) {
 		return false;
 	}