diff --git a/sop-java-picocli/src/main/java/sop/cli/picocli/commands/ExtractCertCmd.java b/sop-java-picocli/src/main/java/sop/cli/picocli/commands/ExtractCertCmd.java
deleted file mode 100644
index 64a7a84..0000000
--- a/sop-java-picocli/src/main/java/sop/cli/picocli/commands/ExtractCertCmd.java
+++ /dev/null
@@ -1,43 +0,0 @@
-// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
-//
-// SPDX-License-Identifier: Apache-2.0
-
-package sop.cli.picocli.commands;
-
-import java.io.IOException;
-
-import picocli.CommandLine;
-import sop.Ready;
-import sop.cli.picocli.SopCLI;
-import sop.exception.SOPGPException;
-import sop.operation.ExtractCert;
-
-@CommandLine.Command(name = "extract-cert",
-        resourceBundle = "msg_extract-cert",
-        exitCodeOnInvalidInput = SOPGPException.UnsupportedOption.EXIT_CODE)
-public class ExtractCertCmd extends AbstractSopCmd {
-
-    @CommandLine.Option(names = "--no-armor",
-            negatable = true)
-    boolean armor = true;
-
-    @Override
-    public void run() {
-        ExtractCert extractCert = throwIfUnsupportedSubcommand(
-                SopCLI.getSop().extractCert(), "extract-cert");
-
-        if (!armor) {
-            extractCert.noArmor();
-        }
-
-        try {
-            Ready ready = extractCert.key(System.in);
-            ready.writeTo(System.out);
-        } catch (IOException e) {
-            throw new RuntimeException(e);
-        } catch (SOPGPException.BadData badData) {
-            String errorMsg = getMsg("sop.error.input.stdin_not_a_private_key");
-            throw new SOPGPException.BadData(errorMsg, badData);
-        }
-    }
-}
diff --git a/sop-java-picocli/src/main/kotlin/sop/cli/picocli/commands/ExtractCertCmd.kt b/sop-java-picocli/src/main/kotlin/sop/cli/picocli/commands/ExtractCertCmd.kt
new file mode 100644
index 0000000..cff996f
--- /dev/null
+++ b/sop-java-picocli/src/main/kotlin/sop/cli/picocli/commands/ExtractCertCmd.kt
@@ -0,0 +1,40 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package sop.cli.picocli.commands
+
+import java.io.IOException
+import picocli.CommandLine.Command
+import picocli.CommandLine.Option
+import sop.cli.picocli.SopCLI
+import sop.exception.SOPGPException
+import sop.exception.SOPGPException.BadData
+
+@Command(
+    name = "extract-cert",
+    resourceBundle = "msg_extract-cert",
+    exitCodeOnInvalidInput = SOPGPException.UnsupportedOption.EXIT_CODE)
+class ExtractCertCmd : AbstractSopCmd() {
+
+    @Option(names = ["--no-armor"], negatable = true) var armor = true
+
+    override fun run() {
+        val extractCert =
+            throwIfUnsupportedSubcommand(SopCLI.getSop().extractCert(), "extract-cert")
+
+        if (!armor) {
+            extractCert.noArmor()
+        }
+
+        try {
+            val ready = extractCert.key(System.`in`)
+            ready.writeTo(System.out)
+        } catch (e: IOException) {
+            throw RuntimeException(e)
+        } catch (badData: BadData) {
+            val errorMsg = getMsg("sop.error.input.stdin_not_a_private_key")
+            throw BadData(errorMsg, badData)
+        }
+    }
+}