Index: trunk/test/unit/org/openstreetmap/josm/gui/autofilter/AutoFilterManagerTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/gui/autofilter/AutoFilterManagerTest.java	(revision 15760)
+++ trunk/test/unit/org/openstreetmap/josm/gui/autofilter/AutoFilterManagerTest.java	(revision 15764)
@@ -3,13 +3,13 @@
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
 
 import java.util.Arrays;
-import java.util.Set;
 import java.util.TreeSet;
-import java.util.function.Consumer;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import org.junit.Rule;
 import org.junit.Test;
-import org.openstreetmap.josm.data.osm.OsmPrimitive;
 import org.openstreetmap.josm.data.osm.OsmUtils;
 import org.openstreetmap.josm.testutils.JOSMTestRules;
@@ -30,11 +30,9 @@
 
     /**
-     * Unit test of {@link AutoFilterManager#getTagValuesConsumer}.
+     * Unit test of {@link AutoFilterManager#getTagValuesForPrimitive}.
      */
     @Test
-    public void testTagValuesConsumer() {
-        Set<String> values = new TreeSet<>();
-        Consumer<OsmPrimitive> consumer = AutoFilterManager.getTagValuesConsumer("level", values);
-        Arrays.asList(
+    public void testTagValuesForPrimitive() {
+        final TreeSet<String> values = Stream.of(
                 OsmUtils.createPrimitive("way level=-4--5"),
                 OsmUtils.createPrimitive("way level=-2"),
@@ -43,7 +41,30 @@
                 OsmUtils.createPrimitive("way level=2;3"),
                 OsmUtils.createPrimitive("way level=6-9"),
-                OsmUtils.createPrimitive("way level=10;12-13")
-                ).forEach(consumer);
+                OsmUtils.createPrimitive("way level=10;12-13"))
+                .flatMap(o -> AutoFilterManager.getTagValuesForPrimitive("level", o))
+                .collect(Collectors.toCollection(TreeSet::new));
         assertEquals(new TreeSet<>(Arrays.asList("-5", "-4", "-2", "0", "1", "2", "3", "6", "7", "8", "9", "10", "12", "13")), values);
+
+    }
+
+    /**
+     * Unit test of {@link AutoFilterManager#getTagValuesForPrimitive} provides sensible defaults, see #17496.
+     */
+    @Test
+    public void testTagValuesForPrimitivesDefaults() {
+        assertNull(getLayer("way foo=bar"));
+        assertEquals("1", getLayer("way bridge=yes"));
+        assertEquals("1", getLayer("way power=line"));
+        assertEquals("-1", getLayer("way tunnel=yes"));
+        assertEquals("0", getLayer("way tunnel=building_passage"));
+        assertEquals("0", getLayer("way highway=residential"));
+        assertEquals("0", getLayer("way railway=rail"));
+        assertEquals("0", getLayer("way waterway=canal"));
+    }
+
+    private String getLayer(final String assertion) {
+        return AutoFilterManager.getTagValuesForPrimitive("layer", OsmUtils.createPrimitive(assertion))
+                .findFirst()
+                .orElse(null);
     }
 }