diff --git a/org.eclipse.scanning.api/src/org/eclipse/scanning/api/filter/Filter.java b/org.eclipse.scanning.api/src/org/eclipse/scanning/api/filter/Filter.java
index a7cc1a03d..fb6df74e5 100644
--- a/org.eclipse.scanning.api/src/org/eclipse/scanning/api/filter/Filter.java
+++ b/org.eclipse.scanning.api/src/org/eclipse/scanning/api/filter/Filter.java
@@ -12,8 +12,11 @@
 package org.eclipse.scanning.api.filter;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
+import java.util.HashSet;
 import java.util.List;
+import java.util.stream.Collectors;
 
 /**
  * A springable class which encapsulates information for a given feature.
@@ -138,7 +141,17 @@ public List<String> filter(final Collection<String> items) {
 		Collection<String> excludes = match(getExcludes(), items);
 		ret.removeAll(excludes);
 		Collection<String> includes = match(getIncludes(), items);
-		ret.addAll(includes);
+		
+		Collection<String> done = new HashSet<>();
+		for (final String item : includes) {
+			
+			if (done.contains(item)) continue;
+			int ecount = (int)ret.stream().filter(t->t.equals(item)).count();
+			int icount = (int)includes.stream().filter(t->t.equals(item)).count();
+			ret.addAll(Arrays.stream(new String[icount-ecount]).map(nothing->item).collect(Collectors.toList()));
+			
+			done.add(item);
+		}
 
 		return ret;
 	}
diff --git a/org.eclipse.scanning.test/src/org/eclipse/scanning/test/filter/FilterTest.java b/org.eclipse.scanning.test/src/org/eclipse/scanning/test/filter/FilterTest.java
index 14a348d6c..1eb49c000 100644
--- a/org.eclipse.scanning.test/src/org/eclipse/scanning/test/filter/FilterTest.java
+++ b/org.eclipse.scanning.test/src/org/eclipse/scanning/test/filter/FilterTest.java
@@ -16,8 +16,10 @@
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.stream.Collectors;
 
 import org.eclipse.scanning.api.device.IScannableDeviceService;
 import org.eclipse.scanning.api.filter.Filter;
@@ -26,9 +28,13 @@
 import org.eclipse.scanning.api.scan.ScanningException;
 import org.eclipse.scanning.example.scannable.MockScannableConnector;
 import org.eclipse.scanning.server.application.PseudoSpringParser;
+import org.junit.Before;
 import org.junit.BeforeClass;
+import org.junit.FixMethodOrder;
 import org.junit.Test;
+import org.junit.runners.MethodSorters;
 
+@FixMethodOrder(MethodSorters.NAME_ASCENDING)
 public class FilterTest {
 	
 	private static IScannableDeviceService sservice;
@@ -41,6 +47,13 @@ public static void parseSpring() throws Exception {
 		sservice = new MockScannableConnector(null);
 	}
 	
+	@Before
+	public void before() throws Exception {
+		fservice.clear();
+		PseudoSpringParser parser = new PseudoSpringParser();
+		parser.parse(FilterTest.class.getResourceAsStream("test_filters.xml"));
+	}
+	
 	@Test
 	public void notNull() {
 		assertNotNull(IFilterService.DEFAULT);
@@ -50,17 +63,12 @@ public void notNull() {
 	}
 	
 	@Test
-	public void noFilter() throws ScanningException {
+	public void znoFilter() throws ScanningException {
 		assertEquals(sservice.getScannableNames(), fservice.filter("not.there", sservice.getScannableNames()));
 	}
 	
 	@Test
 	public void testFilterSpring() throws Exception {
-		
-		fservice.clear();
-		PseudoSpringParser parser = new PseudoSpringParser();
-		parser.parse(FilterTest.class.getResourceAsStream("test_filters.xml"));
-		
 		check();
 	}
 
@@ -78,6 +86,105 @@ public void testFilterManual() throws Exception {
 		
 		check();
 	}
+	
+	@Test
+	public void testDuplicatesNoSpring() throws Exception {
+
+		fservice.clear();
+		
+		IFilter<String> dfilter = new Filter();
+		dfilter.setName("duplicates");
+		dfilter.setIncludes(Arrays.asList("a"));
+		dfilter.setExcludes(Arrays.asList("b"));
+		fservice.register(dfilter);
+	
+		List<String> items = new ArrayList<>(Arrays.asList("a", "a", "b", "b"));
+		assertEquals(Arrays.asList("a", "a"), fservice.filter("duplicates", items));
+		
+		items = new ArrayList<>(Arrays.asList("a", "b", "a", "b"));
+		assertEquals(Arrays.asList("a", "a"), fservice.filter("duplicates", items));
+
+		items = new ArrayList<>(Arrays.asList("b", "b", "1", "a", "a"));
+		assertEquals(Arrays.asList("1", "a", "a"), fservice.filter("duplicates", items));
+		
+		items = new ArrayList<>(Arrays.asList("b", "b", "a", "a", "1"));
+		assertEquals(Arrays.asList("a", "a", "1"), fservice.filter("duplicates", items));
+
+	}
+	
+	@Test
+	public void testDuplicatesExclude() throws Exception {
+
+		fservice.clear();
+		
+		IFilter<String> dfilter = new Filter();
+		dfilter.setName("duplicates");
+		dfilter.setIncludes(Arrays.asList("a"));
+		dfilter.setExcludes(Arrays.asList("a", "b"));
+		fservice.register(dfilter);
+	
+		List<String> items = new ArrayList<>(Arrays.asList("a", "a", "b", "b"));
+		assertEquals(Arrays.asList("a", "a"), fservice.filter("duplicates", items));
+		
+		items = new ArrayList<>(Arrays.asList("a", "b", "a", "b"));
+		assertEquals(Arrays.asList("a", "a"), fservice.filter("duplicates", items));
+
+		items = new ArrayList<>(Arrays.asList("b", "b", "1", "a", "a"));
+		assertEquals(Arrays.asList("1", "a", "a"), fservice.filter("duplicates", items));
+		
+		items = new ArrayList<>(Arrays.asList("b", "b", "a", "a", "1"));
+		
+		// Because we excluded it the result changes
+		assertEquals(Arrays.asList("1", "a", "a"), fservice.filter("duplicates", items));
+
+	}
+
+	@Test(timeout=10000) // Must complete in 10s or less
+	public void testDuplicatesLarge() throws Exception {
+
+		fservice.clear();
+		
+		IFilter<String> dfilter = new Filter();
+		dfilter.setName("duplicates");
+		
+		List<String> as = Arrays.stream(new String[1000]).map(nothing->"a").collect(Collectors.toList());
+		assertEquals(1000, as.size());
+		dfilter.setIncludes(as);
+		List<String> bs = Arrays.stream(new String[1000]).map(nothing->"b").collect(Collectors.toList());
+		assertEquals(1000, bs.size());
+		dfilter.setExcludes(bs);
+		fservice.register(dfilter);
+	
+		List<String> items = new ArrayList<>();
+		items.addAll(as);
+		items.addAll(bs);
+		assertEquals(as, fservice.filter("duplicates", items));
+		
+		items = new ArrayList<>();
+		for (int i = 0; i < 1000; i++) {
+		    items.add(as.get(i));
+		    items.add(bs.get(i));
+		}
+		assertEquals(as, fservice.filter("duplicates", items));
+
+		items = new ArrayList<>();
+		items.addAll(bs);
+		items.add("1");
+		items.addAll(as);
+		assertEquals("1", fservice.filter("duplicates", items).get(0));
+		assertEquals("a", fservice.filter("duplicates", items).get(1));
+		assertEquals("a", fservice.filter("duplicates", items).get(2));
+		
+		items = new ArrayList<>();
+		items.addAll(bs);
+		items.addAll(as);
+		items.add("1");
+		List<String> filtered = fservice.filter("duplicates", items);
+		assertEquals("1", filtered.get(filtered.size()-1));
+		assertEquals("a", filtered.get(filtered.size()-2));
+		assertEquals("a", filtered.get(filtered.size()-3));
+
+	}
 
 	private void check() throws ScanningException {