diff --git a/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/PolicyTags.java b/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/PolicyTags.java
index a78fa92fb..a66be88e1 100644
--- a/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/PolicyTags.java
+++ b/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/PolicyTags.java
@@ -60,6 +60,10 @@ com.google.api.services.bigquery.model.TableFieldSchema.PolicyTags toPb() {
 
   static PolicyTags fromPb(
       com.google.api.services.bigquery.model.TableFieldSchema.PolicyTags tagPb) {
-    return newBuilder().setNames(tagPb.getNames()).build();
+    // Treat a PolicyTag message without a Names subfield as invalid.
+    if (tagPb.getNames() != null) {
+      return newBuilder().setNames(tagPb.getNames()).build();
+    }
+    return null;
   }
 }
diff --git a/google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/PolicyTagsTest.java b/google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/PolicyTagsTest.java
index 2136b2dab..f23cb36c2 100644
--- a/google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/PolicyTagsTest.java
+++ b/google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/PolicyTagsTest.java
@@ -18,6 +18,7 @@
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertNull;
 
 import com.google.common.collect.ImmutableList;
 import java.util.List;
@@ -46,6 +47,13 @@ public void testBuilder() {
     assertNotEquals(POLICY_TAGS, POLICIES);
   }
 
+  @Test
+  public void testWithoutNames() {
+    com.google.api.services.bigquery.model.TableFieldSchema.PolicyTags PARTIALTAG =
+        new com.google.api.services.bigquery.model.TableFieldSchema.PolicyTags();
+    assertNull(PolicyTags.fromPb(PARTIALTAG));
+  }
+
   @Test
   public void testFromAndPb() {
     assertEquals(POLICY_TAGS, PolicyTags.fromPb(POLICY_TAGS.toPb()));