diff --git a/modules/programs/git.nix b/modules/programs/git.nix
index 3061feff7..d344baab6 100644
--- a/modules/programs/git.nix
+++ b/modules/programs/git.nix
@@ -38,6 +38,17 @@ let
         defaultText = "\${pkgs.gnupg}/bin/gpg2";
         description = "Path to GnuPG binary to use.";
       };
+
+      gpgFormat = mkOption {
+        type = types.str;
+        default = "openpgp";
+        defaultText = "openpgp";
+        description = ''
+          Specifies which key format to use when signing with
+          --gpg-sign. Default is "openpgp". Other possible values
+          are "x509", "ssh".
+        '';
+      };
     };
   };
 
@@ -421,6 +432,7 @@ in {
         commit.gpgSign = mkDefault cfg.signing.signByDefault;
         tag.gpgSign = mkDefault cfg.signing.signByDefault;
         gpg.program = cfg.signing.gpgPath;
+        gpg.format = cfg.signing.gpgFormat;
       };
     })
 
diff --git a/tests/modules/programs/git/git-expected.conf b/tests/modules/programs/git/git-expected.conf
index 61e0a2cc5..4dacc7ecd 100644
--- a/tests/modules/programs/git/git-expected.conf
+++ b/tests/modules/programs/git/git-expected.conf
@@ -38,6 +38,7 @@
 	smudge = "git-lfs smudge -- %f"
 
 [gpg]
+	format = "ssh"
 	program = "path-to-gpg"
 
 [interactive]
diff --git a/tests/modules/programs/git/git.nix b/tests/modules/programs/git/git.nix
index fb949be00..cc6496480 100644
--- a/tests/modules/programs/git/git.nix
+++ b/tests/modules/programs/git/git.nix
@@ -55,6 +55,7 @@ in {
           }
         ];
         signing = {
+          gpgFormat = "ssh";
           gpgPath = "path-to-gpg";
           key = "00112233445566778899AABBCCDDEEFF";
           signByDefault = true;