diff --git a/pkgs/development/libraries/kerberos/heimdal.nix b/pkgs/development/libraries/kerberos/heimdal.nix
index c9dd28cd396..aeea290bdb2 100644
--- a/pkgs/development/libraries/kerberos/heimdal.nix
+++ b/pkgs/development/libraries/kerberos/heimdal.nix
@@ -50,4 +50,6 @@ stdenv.mkDerivation rec {
     platforms = platforms.linux;
     maintainers = with maintainers; [ wkennington ];
   };
+
+  passthru.implementation = "heimdal";
 }
diff --git a/pkgs/development/libraries/kerberos/krb5.nix b/pkgs/development/libraries/kerberos/krb5.nix
index d4e4a59ec5f..74d26d2fa03 100644
--- a/pkgs/development/libraries/kerberos/krb5.nix
+++ b/pkgs/development/libraries/kerberos/krb5.nix
@@ -34,4 +34,6 @@ stdenv.mkDerivation (rec {
     platforms = platforms.unix;
     maintainers = with maintainers; [ wkennington ];
   };
+
+  passthru.implementation = "krb5";
 })