diff --git a/src/main/java/org/kohsuke/github/GHMilestone.java b/src/main/java/org/kohsuke/github/GHMilestone.java
index 7cd556c8ee..74615951be 100644
--- a/src/main/java/org/kohsuke/github/GHMilestone.java
+++ b/src/main/java/org/kohsuke/github/GHMilestone.java
@@ -1,13 +1,14 @@
 package org.kohsuke.github;
 
 import com.infradna.tool.bridge_method_injector.WithBridgeMethods;
+import edu.umd.cs.findbugs.annotations.CheckForNull;
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import org.kohsuke.github.internal.EnumUtils;
 
 import java.io.IOException;
 import java.net.URL;
 import java.time.Instant;
 import java.util.Date;
-import java.util.Locale;
 
 // TODO: Auto-generated Javadoc
 /**
@@ -141,10 +142,11 @@ public GHRepository getOwner() {
     /**
      * Gets state.
      *
-     * @return the state
+     * @return the state, or {@code null} if the state is not available
      */
+    @CheckForNull
     public GHMilestoneState getState() {
-        return Enum.valueOf(GHMilestoneState.class, state.toUpperCase(Locale.ENGLISH));
+        return EnumUtils.getNullableEnumOrDefault(GHMilestoneState.class, state, GHMilestoneState.UNKNOWN);
     }
 
     /**
diff --git a/src/main/java/org/kohsuke/github/GHMilestoneState.java b/src/main/java/org/kohsuke/github/GHMilestoneState.java
index ab2030239d..4cba5d7bd2 100644
--- a/src/main/java/org/kohsuke/github/GHMilestoneState.java
+++ b/src/main/java/org/kohsuke/github/GHMilestoneState.java
@@ -11,5 +11,7 @@ public enum GHMilestoneState {
     /** The closed. */
     CLOSED,
     /** The open. */
-    OPEN
+    OPEN,
+    /** The unknown. */
+    UNKNOWN
 }
diff --git a/src/test/java/org/kohsuke/github/EnumTest.java b/src/test/java/org/kohsuke/github/EnumTest.java
index 7805ad2575..b008c488ed 100644
--- a/src/test/java/org/kohsuke/github/EnumTest.java
+++ b/src/test/java/org/kohsuke/github/EnumTest.java
@@ -64,7 +64,7 @@ public void touchEnums() {
 
         assertThat(GHMembership.Role.values().length, equalTo(2));
 
-        assertThat(GHMilestoneState.values().length, equalTo(2));
+        assertThat(GHMilestoneState.values().length, equalTo(3));
 
         assertThat(GHMyself.RepositoryListFilter.values().length, equalTo(5));
 
diff --git a/src/test/java/org/kohsuke/github/GHIssueEventAttributeTest.java b/src/test/java/org/kohsuke/github/GHIssueEventAttributeTest.java
index 152e377311..c11f0e6b96 100644
--- a/src/test/java/org/kohsuke/github/GHIssueEventAttributeTest.java
+++ b/src/test/java/org/kohsuke/github/GHIssueEventAttributeTest.java
@@ -14,6 +14,7 @@
 import static java.util.stream.Collectors.toList;
 import static org.hamcrest.Matchers.hasSize;
 import static org.hamcrest.Matchers.notNullValue;
+import static org.hamcrest.Matchers.nullValue;
 
 // TODO: Auto-generated Javadoc
 /**
@@ -24,7 +25,10 @@ public class GHIssueEventAttributeTest extends AbstractGitHubWireMockTest {
     private enum Type implements Predicate<GHIssueEvent>, Consumer<GHIssueEvent> {
         assignment(e -> assertThat(e.getAssignee(), notNullValue()), "assigned", "unassigned"),
         label(e -> assertThat(e.getLabel(), notNullValue()), "labeled", "unlabeled"),
-        milestone(e -> assertThat(e.getMilestone(), notNullValue()), "milestoned", "demilestoned");
+        milestone(e -> {
+            assertThat(e.getMilestone(), notNullValue());
+            assertThat(e.getMilestone().getState(), nullValue());
+        }, "milestoned", "demilestoned");
 
         private final Consumer<GHIssueEvent> assertion;
         private final Set<String> subtypes;