diff --git a/src/security/identity-certificate.cpp b/src/security/identity-certificate.cpp
index 1eaceac..7a7180d 100644
--- a/src/security/identity-certificate.cpp
+++ b/src/security/identity-certificate.cpp
@@ -68,7 +68,7 @@
 IdentityCertificate::isCorrectName(const Name& name)
 {
   string idString("ID-CERT");
-  int i = name.size() - 1;
+  ssize_t i = name.size() - 1;
   for (; i >= 0; i--) {
     if (name.get(i).toUri() == idString)
       break;