diff --git a/sop-java-picocli/src/main/java/sop/cli/picocli/SOPExceptionExitCodeMapper.java b/sop-java-picocli/src/main/java/sop/cli/picocli/SOPExceptionExitCodeMapper.java
deleted file mode 100644
index 8b38af3..0000000
--- a/sop-java-picocli/src/main/java/sop/cli/picocli/SOPExceptionExitCodeMapper.java
+++ /dev/null
@@ -1,34 +0,0 @@
-// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
-//
-// SPDX-License-Identifier: Apache-2.0
-
-package sop.cli.picocli;
-
-import picocli.CommandLine;
-import sop.exception.SOPGPException;
-
-public class SOPExceptionExitCodeMapper implements CommandLine.IExitCodeExceptionMapper {
-
-    @Override
-    public int getExitCode(Throwable exception) {
-        if (exception instanceof SOPGPException) {
-            return ((SOPGPException) exception).getExitCode();
-        }
-        if (exception instanceof CommandLine.UnmatchedArgumentException) {
-            CommandLine.UnmatchedArgumentException ex = (CommandLine.UnmatchedArgumentException) exception;
-            // Unmatched option of subcommand (eg. `generate-key -k`)
-            if (ex.isUnknownOption()) {
-                return SOPGPException.UnsupportedOption.EXIT_CODE;
-            }
-            // Unmatched subcommand
-            return SOPGPException.UnsupportedSubcommand.EXIT_CODE;
-        }
-        // Invalid option (eg. `--label Invalid`)
-        if (exception instanceof CommandLine.ParameterException) {
-            return SOPGPException.UnsupportedOption.EXIT_CODE;
-        }
-
-        // Others, like IOException etc.
-        return 1;
-    }
-}
diff --git a/sop-java-picocli/src/main/kotlin/sop/cli/picocli/SOPExceptionExitCodeMapper.kt b/sop-java-picocli/src/main/kotlin/sop/cli/picocli/SOPExceptionExitCodeMapper.kt
new file mode 100644
index 0000000..29aa77b
--- /dev/null
+++ b/sop-java-picocli/src/main/kotlin/sop/cli/picocli/SOPExceptionExitCodeMapper.kt
@@ -0,0 +1,31 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package sop.cli.picocli
+
+import picocli.CommandLine.*
+import sop.exception.SOPGPException
+
+class SOPExceptionExitCodeMapper : IExitCodeExceptionMapper {
+
+    override fun getExitCode(exception: Throwable): Int =
+        if (exception is SOPGPException) {
+            // SOPGPExceptions have well-defined exit code
+            exception.getExitCode()
+        } else if (exception is UnmatchedArgumentException) {
+            if (exception.isUnknownOption) {
+                // Unmatched option of subcommand (e.g. `generate-key --unknown`)
+                SOPGPException.UnsupportedOption.EXIT_CODE
+            } else {
+                // Unmatched subcommand
+                SOPGPException.UnsupportedSubcommand.EXIT_CODE
+            }
+        } else if (exception is ParameterException) {
+            // Invalid option (e.g. `--as invalid`)
+            SOPGPException.UnsupportedOption.EXIT_CODE
+        } else {
+            // Others, like IOException etc.
+            1
+        }
+}