diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/CollectionBinder.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/CollectionBinder.java
index ac953607dd..16f8e71379 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/CollectionBinder.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/CollectionBinder.java
@@ -65,18 +65,27 @@ class CollectionBinder extends IndexedElementsBinder<Collection<Object>> {
 		try {
 			existingCollection.clear();
 			existingCollection.addAll(additional);
-			return existingCollection;
+			return copyIfPossible(existingCollection);
 		}
 		catch (UnsupportedOperationException ex) {
 			return createNewCollection(additional);
 		}
 	}
 
-	private Collection<Object> createNewCollection(Collection<Object> additional) {
-		Collection<Object> merged = CollectionFactory
-				.createCollection(additional.getClass(), additional.size());
-		merged.addAll(additional);
-		return merged;
+	private Collection<Object> copyIfPossible(Collection<Object> collection) {
+		try {
+			return createNewCollection(collection);
+		}
+		catch (Exception ex) {
+			return collection;
+		}
+	}
+
+	private Collection<Object> createNewCollection(Collection<Object> collection) {
+		Collection<Object> result = CollectionFactory
+				.createCollection(collection.getClass(), collection.size());
+		result.addAll(collection);
+		return result;
 	}
 
 }
diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/MapBinder.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/MapBinder.java
index 1d02a1020f..5ad55455b4 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/MapBinder.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/MapBinder.java
@@ -91,7 +91,19 @@ class MapBinder extends AggregateBinder<Map<Object, Object>> {
 			return additional;
 		}
 		existingMap.putAll(additional);
-		return existingMap;
+		return copyIfPossible(existingMap);
+	}
+
+	private Map<Object, Object> copyIfPossible(Map<Object, Object> map) {
+		try {
+			Map<Object, Object> result = CollectionFactory.createMap(map.getClass(),
+					map.size());
+			result.putAll(map);
+			return result;
+		}
+		catch (Exception ex) {
+			return map;
+		}
 	}
 
 	private class EntryBinder {
diff --git a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/CollectionBinderTests.java b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/CollectionBinderTests.java
index 06fe47f936..3ceeff8dd7 100644
--- a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/CollectionBinderTests.java
+++ b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/CollectionBinderTests.java
@@ -172,7 +172,6 @@ public class CollectionBinderTests {
 		List<Integer> result = this.binder
 				.bind("foo", INTEGER_LIST.withExistingValue(existing)).get();
 		assertThat(result).isExactlyInstanceOf(LinkedList.class);
-		assertThat(result).isSameAs(existing);
 		assertThat(result).containsExactly(1);
 	}
 
@@ -309,7 +308,20 @@ public class CollectionBinderTests {
 		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
 		source.put("foo.items", "a,b,c,c");
 		this.sources.add(source);
-		ExampleCustomBean result = this.binder.bind("foo", ExampleCustomBean.class).get();
+		ExampleCustomNoDefaultConstructorBean result = this.binder
+				.bind("foo", ExampleCustomNoDefaultConstructorBean.class).get();
+		assertThat(result.getItems()).hasSize(4);
+		assertThat(result.getItems()).containsExactly("a", "b", "c", "c");
+	}
+
+	@Test
+	public void bindToCollectionWithDefaultConstructor() {
+		// gh-12322
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("foo.items", "a,b,c,c");
+		this.sources.add(source);
+		ExampleCustomWithDefaultConstructorBean result = this.binder
+				.bind("foo", ExampleCustomWithDefaultConstructorBean.class).get();
 		assertThat(result.getItems()).hasSize(4);
 		assertThat(result.getItems()).containsExactly("a", "b", "c", "c");
 	}
@@ -415,31 +427,46 @@ public class CollectionBinderTests {
 		}
 	}
 
-	public static class ExampleCustomBean {
+	public static class ExampleCustomNoDefaultConstructorBean {
 
-		private MyCustomList items = new MyCustomList(Collections.singletonList("foo"));
+		private MyCustomNoDefaultConstructorList items = new MyCustomNoDefaultConstructorList(
+				Collections.singletonList("foo"));
 
-		public MyCustomList getItems() {
+		public MyCustomNoDefaultConstructorList getItems() {
 			return this.items;
 		}
 
-		public void setItems(MyCustomList items) {
+		public void setItems(MyCustomNoDefaultConstructorList items) {
 			this.items = items;
 		}
+
 	}
 
-	public static class MyCustomList extends ArrayList<String> {
+	public static class MyCustomNoDefaultConstructorList extends ArrayList<String> {
 
-		private List<String> items;
-
-		public MyCustomList(List<String> items) {
-			this.items = items;
+		public MyCustomNoDefaultConstructorList(List<String> items) {
+			addAll(items);
 		}
 
-		public List<String> getItems() {
+	}
+
+	public static class ExampleCustomWithDefaultConstructorBean {
+
+		private MyCustomWithDefaultConstructorList items = new MyCustomWithDefaultConstructorList();
+
+		public MyCustomWithDefaultConstructorList getItems() {
 			return this.items;
 		}
 
+		public void setItems(MyCustomWithDefaultConstructorList items) {
+			this.items.clear();
+			this.items.addAll(items);
+		}
+
+	}
+
+	public static class MyCustomWithDefaultConstructorList extends ArrayList<String> {
+
 	}
 
 	public static class BeanWithNestedCollection {
diff --git a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/MapBinderTests.java b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/MapBinderTests.java
index f56fa71667..ea4553e9c3 100644
--- a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/MapBinderTests.java
+++ b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/MapBinderTests.java
@@ -261,7 +261,6 @@ public class MapBinderTests {
 				.withExistingValue(existing);
 		Map<String, Integer> result = this.binder.bind("foo", target).get();
 		assertThat(result).isExactlyInstanceOf(HashMap.class);
-		assertThat(result).isSameAs(existing);
 		assertThat(result).hasSize(2);
 		assertThat(result).containsEntry("bar", 1);
 		assertThat(result).containsEntry("baz", 1001);
@@ -595,6 +594,27 @@ public class MapBinderTests {
 		assertThat(map).containsExactly(entry("bar", RuntimeException.class));
 	}
 
+	@Test
+	public void bindToMapWithNoDefaultConstructor() {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("foo.items.a", "b");
+		this.sources.add(source);
+		ExampleCustomNoDefaultConstructorBean result = this.binder
+				.bind("foo", ExampleCustomNoDefaultConstructorBean.class).get();
+		assertThat(result.getItems()).containsOnly(entry("foo", "bar"), entry("a", "b"));
+	}
+
+	@Test
+	public void bindToMapWithDefaultConstructor() {
+		// gh-12322
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("foo.items.a", "b");
+		this.sources.add(source);
+		ExampleCustomWithDefaultConstructorBean result = this.binder
+				.bind("foo", ExampleCustomWithDefaultConstructorBean.class).get();
+		assertThat(result.getItems()).containsExactly(entry("a", "b"));
+	}
+
 	private <K, V> Bindable<Map<K, V>> getMapBindable(Class<K> keyGeneric,
 			ResolvableType valueType) {
 		ResolvableType keyType = ResolvableType.forClass(keyGeneric);
@@ -657,4 +677,47 @@ public class MapBinderTests {
 
 	}
 
+	public static class ExampleCustomNoDefaultConstructorBean {
+
+		private MyCustomNoDefaultConstructorList items = new MyCustomNoDefaultConstructorList(
+				Collections.singletonMap("foo", "bar"));
+
+		public MyCustomNoDefaultConstructorList getItems() {
+			return this.items;
+		}
+
+		public void setItems(MyCustomNoDefaultConstructorList items) {
+			this.items = items;
+		}
+
+	}
+
+	public static class MyCustomNoDefaultConstructorList extends HashMap<String, String> {
+
+		public MyCustomNoDefaultConstructorList(Map<String, String> items) {
+			putAll(items);
+		}
+
+	}
+
+	public static class ExampleCustomWithDefaultConstructorBean {
+
+		private MyCustomWithDefaultConstructorList items = new MyCustomWithDefaultConstructorList();
+
+		public MyCustomWithDefaultConstructorList getItems() {
+			return this.items;
+		}
+
+		public void setItems(MyCustomWithDefaultConstructorList items) {
+			this.items.clear();
+			this.items.putAll(items);
+		}
+
+	}
+
+	public static class MyCustomWithDefaultConstructorList
+			extends HashMap<String, String> {
+
+	}
+
 }