diff --git a/pgpainless-core/src/main/java/org/pgpainless/key/generation/KeySpec.java b/pgpainless-core/src/main/java/org/pgpainless/key/generation/KeySpec.java
index 5572f449..c53d91e8 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/key/generation/KeySpec.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/key/generation/KeySpec.java
@@ -55,7 +55,7 @@ public class KeySpec {
         return inheritedSubPackets;
     }
 
-    public static KeySpecBuilder getBuilder(KeyType type, KeyFlag... flags) {
-        return new KeySpecBuilder(type, flags);
+    public static KeySpecBuilder getBuilder(KeyType type, KeyFlag flag, KeyFlag... flags) {
+        return new KeySpecBuilder(type, flag, flags);
     }
 }
diff --git a/pgpainless-core/src/main/java/org/pgpainless/key/generation/KeySpecBuilder.java b/pgpainless-core/src/main/java/org/pgpainless/key/generation/KeySpecBuilder.java
index bbc7f14a..d6095201 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/key/generation/KeySpecBuilder.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/key/generation/KeySpecBuilder.java
@@ -30,6 +30,7 @@ import org.pgpainless.algorithm.HashAlgorithm;
 import org.pgpainless.algorithm.KeyFlag;
 import org.pgpainless.algorithm.SymmetricKeyAlgorithm;
 import org.pgpainless.key.generation.type.KeyType;
+import org.pgpainless.util.CollectionUtils;
 
 public class KeySpecBuilder implements KeySpecBuilderInterface {
 
@@ -41,10 +42,14 @@ public class KeySpecBuilder implements KeySpecBuilderInterface {
     private Set<HashAlgorithm> preferredHashAlgorithms = algorithmSuite.getHashAlgorithms();
     private Set<SymmetricKeyAlgorithm> preferredSymmetricAlgorithms = algorithmSuite.getSymmetricKeyAlgorithms();
 
-    KeySpecBuilder(@Nonnull KeyType type, KeyFlag... flags) {
-        if (flags == null || flags.length == 0) {
-            throw new IllegalArgumentException("KeyFlags cannot be empty.");
+    KeySpecBuilder(@Nonnull KeyType type, KeyFlag flag, KeyFlag... flags) {
+        if (flag == null) {
+            throw new IllegalArgumentException("Key MUST carry at least one key flag");
         }
+        if (flags == null) {
+            throw new IllegalArgumentException("List of additional flags MUST NOT be null.");
+        }
+        flags = CollectionUtils.concat(flag, flags);
         assureKeyCanCarryFlags(type, flags);
         this.type = type;
         this.keyFlags = flags;
diff --git a/pgpainless-core/src/main/java/org/pgpainless/util/CollectionUtils.java b/pgpainless-core/src/main/java/org/pgpainless/util/CollectionUtils.java
index 6ad81991..cb845df4 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/util/CollectionUtils.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/util/CollectionUtils.java
@@ -15,6 +15,7 @@
  */
 package org.pgpainless.util;
 
+import java.lang.reflect.Array;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
@@ -33,4 +34,11 @@ public final class CollectionUtils {
         }
         return items;
     }
+
+    public static <T> T[] concat(T t, T[] ts) {
+        T[] concat = (T[]) Array.newInstance(t.getClass(), ts.length + 1);
+        concat[0] = t;
+        System.arraycopy(ts, 0, concat, 1, ts.length);
+        return concat;
+    }
 }