diff --git a/external-sop/src/main/java/sop/external/operation/ArmorExternal.java b/external-sop/src/main/java/sop/external/operation/ArmorExternal.java
deleted file mode 100644
index e1d02e9..0000000
--- a/external-sop/src/main/java/sop/external/operation/ArmorExternal.java
+++ /dev/null
@@ -1,46 +0,0 @@
-// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
-//
-// SPDX-License-Identifier: Apache-2.0
-
-package sop.external.operation;
-
-import sop.Ready;
-import sop.enums.ArmorLabel;
-import sop.exception.SOPGPException;
-import sop.external.ExternalSOP;
-import sop.operation.Armor;
-
-import javax.annotation.Nonnull;
-import java.io.InputStream;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Properties;
-
-/**
- * Implementation of the {@link Armor} operation using an external SOP binary.
- */
-public class ArmorExternal implements Armor {
-
-    private final List<String> commandList = new ArrayList<>();
-    private final List<String> envList;
-
-    public ArmorExternal(String binary, Properties environment) {
-        commandList.add(binary);
-        commandList.add("armor");
-        envList = ExternalSOP.propertiesToEnv(environment);
-    }
-
-    @Override
-    @Deprecated
-    @Nonnull
-    public Armor label(@Nonnull ArmorLabel label) throws SOPGPException.UnsupportedOption {
-        commandList.add("--label=" + label);
-        return this;
-    }
-
-    @Override
-    @Nonnull
-    public Ready data(@Nonnull InputStream data) throws SOPGPException.BadData {
-        return ExternalSOP.executeTransformingOperation(Runtime.getRuntime(), commandList, envList, data);
-    }
-}
diff --git a/external-sop/src/main/kotlin/sop/external/operation/ArmorExternal.kt b/external-sop/src/main/kotlin/sop/external/operation/ArmorExternal.kt
new file mode 100644
index 0000000..f80c57b
--- /dev/null
+++ b/external-sop/src/main/kotlin/sop/external/operation/ArmorExternal.kt
@@ -0,0 +1,26 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package sop.external.operation
+
+import java.io.InputStream
+import java.util.Properties
+import sop.Ready
+import sop.enums.ArmorLabel
+import sop.exception.SOPGPException
+import sop.external.ExternalSOP
+import sop.operation.Armor
+
+/** Implementation of the [Armor] operation using an external SOP binary. */
+class ArmorExternal(binary: String, environment: Properties) : Armor {
+
+    private val commandList: MutableList<String> = mutableListOf(binary, "armor")
+    private val envList: List<String> = ExternalSOP.propertiesToEnv(environment)
+
+    override fun label(label: ArmorLabel): Armor = apply { commandList.add("--label=$label") }
+
+    @Throws(SOPGPException.BadData::class)
+    override fun data(data: InputStream): Ready =
+        ExternalSOP.executeTransformingOperation(Runtime.getRuntime(), commandList, envList, data)
+}