diff --git a/pgpainless-core/src/main/kotlin/org/pgpainless/signature/subpackets/SelfSignatureSubpackets.kt b/pgpainless-core/src/main/kotlin/org/pgpainless/signature/subpackets/SelfSignatureSubpackets.kt
index 691b6e6c..39a7dbde 100644
--- a/pgpainless-core/src/main/kotlin/org/pgpainless/signature/subpackets/SelfSignatureSubpackets.kt
+++ b/pgpainless-core/src/main/kotlin/org/pgpainless/signature/subpackets/SelfSignatureSubpackets.kt
@@ -171,9 +171,8 @@ interface SelfSignatureSubpackets : BaseSignatureSubpackets {
 
     fun setFeatures(features: Features?): SelfSignatureSubpackets
 
-    fun getFeatures(): List<Feature> = getFeaturesPacket()
-        ?.let { Feature.fromBitmask(it.features.toInt()) }
-        .orEmpty()
+    fun getFeatures(): List<Feature> =
+        getFeaturesPacket()?.let { Feature.fromBitmask(it.features.toInt()) }.orEmpty()
 
     fun getFeaturesPacket(): Features?
 
diff --git a/pgpainless-core/src/test/kotlin/org/pgpainless/signature/subpackets/SelfSignatureSubpacketCallbackTest.kt b/pgpainless-core/src/test/kotlin/org/pgpainless/signature/subpackets/SelfSignatureSubpacketCallbackTest.kt
new file mode 100644
index 00000000..74daf729
--- /dev/null
+++ b/pgpainless-core/src/test/kotlin/org/pgpainless/signature/subpackets/SelfSignatureSubpacketCallbackTest.kt
@@ -0,0 +1,76 @@
+// SPDX-FileCopyrightText: 2024 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.signature.subpackets
+
+import java.util.*
+import openpgp.toSecondsPrecision
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertNull
+import org.junit.jupiter.api.Assertions.assertTrue
+import org.junit.jupiter.api.Test
+import org.pgpainless.algorithm.Feature
+import org.pgpainless.algorithm.KeyFlag
+
+class SelfSignatureSubpacketCallbackTest {
+
+    @Test
+    fun testSetHashedSignatureCreationTimeViaCallback() {
+        val subpackets: SelfSignatureSubpackets = SignatureSubpackets.createEmptySubpackets()
+        val date = Date().toSecondsPrecision()
+        val callback = SelfSignatureSubpackets.applyHashed { setSignatureCreationTime(date) }
+
+        callback.modifyHashedSubpackets(subpackets)
+
+        assertEquals(subpackets.getSignatureCreationTime(), date)
+    }
+
+    @Test
+    fun testSetUnhashedSignatureCreationTimeViaCallback() {
+        val subpackets: SelfSignatureSubpackets = SignatureSubpackets.createEmptySubpackets()
+        val date = Date().toSecondsPrecision()
+        val callback = SelfSignatureSubpackets.applyUnhashed { setSignatureCreationTime(date) }
+
+        callback.modifyUnhashedSubpackets(subpackets)
+
+        assertEquals(subpackets.getSignatureCreationTime(), date)
+    }
+
+    @Test
+    fun `test that mismatching applyHashed() with modifyUnhashedSubpackets() will not modify the subpackets`() {
+        val subpackets: SelfSignatureSubpackets = SignatureSubpackets.createEmptySubpackets()
+        val callback =
+            SelfSignatureSubpackets.applyHashed {
+                setKeyFlags(KeyFlag.CERTIFY_OTHER)
+                setFeatures(Feature.MODIFICATION_DETECTION)
+            }
+
+        callback.modifyUnhashedSubpackets(subpackets)
+
+        assertNull(subpackets.getKeyFlagsPacket())
+        assertNull(subpackets.getFeaturesPacket())
+    }
+
+    @Test
+    fun testThen() {
+        val subpackets: SelfSignatureSubpackets = SignatureSubpackets.createEmptySubpackets()
+        val firstCallback =
+            SelfSignatureSubpackets.applyHashed {
+                addNotationData(false, "test@pgpainless.org", "foo-bar")
+                setFeatures(Feature.MODIFICATION_DETECTION)
+            }
+        val secondCallback =
+            SelfSignatureSubpackets.applyHashed {
+                clearNotationData()
+                setKeyFlags(KeyFlag.CERTIFY_OTHER)
+            }
+
+        // removes the notation, but preserves the features and adds key-flags
+        firstCallback.then(secondCallback).modifyHashedSubpackets(subpackets)
+
+        assertTrue(subpackets.getNotationDataPackets().isEmpty())
+        assertEquals(listOf(Feature.MODIFICATION_DETECTION), subpackets.getFeatures())
+        assertEquals(listOf(KeyFlag.CERTIFY_OTHER), subpackets.getKeyFlags())
+    }
+}