Index: trunk/test/unit/org/openstreetmap/josm/data/imagery/ImageryInfoTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/data/imagery/ImageryInfoTest.java	(revision 9753)
+++ trunk/test/unit/org/openstreetmap/josm/data/imagery/ImageryInfoTest.java	(revision 9756)
@@ -6,6 +6,7 @@
 import java.util.Arrays;
 import java.util.Collections;
-import java.util.List;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 
 import org.junit.BeforeClass;
@@ -13,4 +14,5 @@
 import org.openstreetmap.josm.JOSMFixture;
 import org.openstreetmap.josm.data.Preferences;
+import org.openstreetmap.josm.tools.MultiMap;
 
 /**
@@ -46,5 +48,7 @@
     public void testSerializeStruct() {
         final ImageryInfo.ImageryPreferenceEntry info = new ImageryInfo.ImageryPreferenceEntry();
-        info.noTileHeaders = Collections.singletonMap("ETag", Arrays.asList("foo", "bar"));
+        info.noTileHeaders = new MultiMap<>();
+        info.noTileHeaders.put("ETag", "foo");
+        info.noTileHeaders.put("ETag", "bar");
         final Map<String, String> map = Preferences.serializeStruct(info, ImageryInfo.ImageryPreferenceEntry.class);
         assertEquals("{noTileHeaders={\"ETag\":[\"foo\",\"bar\"]}}", map.toString());
@@ -58,7 +62,10 @@
         final ImageryInfo.ImageryPreferenceEntry info = Preferences.deserializeStruct(
                 Collections.singletonMap("noTileHeaders", "{\"ETag\":[\"foo\",\"bar\"]}"), ImageryInfo.ImageryPreferenceEntry.class);
-        assertEquals(info.noTileHeaders, Collections.singletonMap("ETag", Arrays.asList("foo", "bar")));
-        final List<String> eTag = info.noTileHeaders.get("ETag");
-        assertEquals(eTag, Arrays.asList("foo", "bar"));
+        MultiMap<String, String> expect = new MultiMap<>();
+        expect.put("ETag", "foo");
+        expect.put("ETag", "bar");
+        assertEquals(info.noTileHeaders, expect);
+        final Set<String> eTag = info.noTileHeaders.get("ETag");
+        assertEquals(eTag, new HashSet<String>(Arrays.asList("foo", "bar")));
     }
 
@@ -70,6 +77,6 @@
         final ImageryInfo.ImageryPreferenceEntry info = Preferences.deserializeStruct(
                 Collections.singletonMap("noTileHeaders", "{\"ETag\":\"foo-and-bar\"}"), ImageryInfo.ImageryPreferenceEntry.class);
-        final List<String> eTag = info.noTileHeaders.get("ETag");
-        assertEquals(eTag, Arrays.asList("foo", "bar"));
+        final Set<String> eTag = info.noTileHeaders.get("ETag");
+        assertEquals(eTag, Collections.singleton("foo-and-bar"));
     }
 }