diff --git a/pgpainless-core/src/test/java/org/pgpainless/key/SubkeyIdentifierTest.java b/pgpainless-core/src/test/java/org/pgpainless/key/SubkeyIdentifierTest.java
index fe792e4d..add18fd5 100644
--- a/pgpainless-core/src/test/java/org/pgpainless/key/SubkeyIdentifierTest.java
+++ b/pgpainless-core/src/test/java/org/pgpainless/key/SubkeyIdentifierTest.java
@@ -5,8 +5,10 @@
 package org.pgpainless.key;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.IOException;
 import java.util.NoSuchElementException;
@@ -102,6 +104,15 @@ public class SubkeyIdentifierTest {
         assertNotEquals(id1, null);
     }
 
+    @Test
+    public void testIsPrimaryKey() {
+        SubkeyIdentifier primaryKey = new SubkeyIdentifier(PRIMARY_FP);
+        assertTrue(primaryKey.isPrimaryKey());
+
+        SubkeyIdentifier subKey = new SubkeyIdentifier(PRIMARY_FP, SUBKEY_FP);
+        assertFalse(subKey.isPrimaryKey());
+    }
+
     @Test
     public void nonExistentSubkeyThrowsNoSuchElementException() {
         assertThrows(NoSuchElementException.class, () -> new SubkeyIdentifier(CERT, 123));