diff --git a/pgpainless-core/src/main/java/org/pgpainless/key/generation/KeyRingBuilder.java b/pgpainless-core/src/main/java/org/pgpainless/key/generation/KeyRingBuilder.java
index 99f3df37..220c5cb7 100644
--- a/pgpainless-core/src/main/java/org/pgpainless/key/generation/KeyRingBuilder.java
+++ b/pgpainless-core/src/main/java/org/pgpainless/key/generation/KeyRingBuilder.java
@@ -201,7 +201,7 @@ public class KeyRingBuilder implements KeyRingBuilderInterface {
 
         @Override
         public WithAdditionalUserIdOrPassphrase withPrimaryUserId(@Nonnull String userId) {
-            KeyRingBuilder.this.userId = userId;
+            KeyRingBuilder.this.userId = userId.trim();
             return new WithAdditionalUserIdOrPassphraseImpl();
         }
 
@@ -215,10 +215,11 @@ public class KeyRingBuilder implements KeyRingBuilderInterface {
 
         @Override
         public WithAdditionalUserIdOrPassphrase withAdditionalUserId(@Nonnull String userId) {
-            if (KeyRingBuilder.this.userId.equals(userId)) {
+            String trimmed = userId.trim();
+            if (KeyRingBuilder.this.userId.equals(trimmed)) {
                 throw new IllegalArgumentException("Additional user-id MUST NOT be equal to primary user-id.");
             }
-            KeyRingBuilder.this.additionalUserIds.add(userId);
+            KeyRingBuilder.this.additionalUserIds.add(trimmed);
             return this;
         }
 
diff --git a/pgpainless-core/src/test/java/org/pgpainless/key/generation/GenerateKeyWithAdditionalUserIdTest.java b/pgpainless-core/src/test/java/org/pgpainless/key/generation/GenerateKeyWithAdditionalUserIdTest.java
index a518cecd..6ab82bb0 100644
--- a/pgpainless-core/src/test/java/org/pgpainless/key/generation/GenerateKeyWithAdditionalUserIdTest.java
+++ b/pgpainless-core/src/test/java/org/pgpainless/key/generation/GenerateKeyWithAdditionalUserIdTest.java
@@ -43,6 +43,7 @@ public class GenerateKeyWithAdditionalUserIdTest {
                 .withPrimaryUserId("primary@user.id")
                 .withAdditionalUserId("additional@user.id")
                 .withAdditionalUserId("additional2@user.id")
+                .withAdditionalUserId("\ttrimThis@user.id     ")
                 .withoutPassphrase()
                 .build();
 
@@ -50,6 +51,7 @@ public class GenerateKeyWithAdditionalUserIdTest {
         assertEquals("primary@user.id", userIds.next());
         assertEquals("additional@user.id", userIds.next());
         assertEquals("additional2@user.id", userIds.next());
+        assertEquals("trimThis@user.id", userIds.next());
         assertFalse(userIds.hasNext());
 
         ByteArrayOutputStream byteOut = new ByteArrayOutputStream();