diff --git a/spring-boot/src/main/java/org/springframework/boot/bind/RelaxedDataBinder.java b/spring-boot/src/main/java/org/springframework/boot/bind/RelaxedDataBinder.java
index db4afff4a8..b4018a6aae 100644
--- a/spring-boot/src/main/java/org/springframework/boot/bind/RelaxedDataBinder.java
+++ b/spring-boot/src/main/java/org/springframework/boot/bind/RelaxedDataBinder.java
@@ -20,10 +20,12 @@ import java.net.InetAddress;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 import org.springframework.beans.BeanWrapper;
 import org.springframework.beans.BeanWrapperImpl;
@@ -139,10 +141,14 @@ public class RelaxedDataBinder extends DataBinder {
 		wrapper.setConversionService(new RelaxedConversionService(getConversionService()));
 		wrapper.setAutoGrowNestedPaths(true);
 		List<PropertyValue> sortedValues = new ArrayList<PropertyValue>();
+		Set<String> modifiedNames = new HashSet<String>();
 		List<String> sortedNames = getSortedPropertyNames(propertyValues);
 		for (String name : sortedNames) {
-			sortedValues.add(modifyProperty(wrapper,
-					propertyValues.getPropertyValue(name)));
+			PropertyValue propertyValue = propertyValues.getPropertyValue(name);
+			PropertyValue modifiedProperty = modifyProperty(wrapper, propertyValue);
+			if (modifiedNames.add(modifiedProperty.getName())) {
+				sortedValues.add(modifiedProperty);
+			}
 		}
 		return new MutablePropertyValues(sortedValues);
 	}
diff --git a/spring-boot/src/test/java/org/springframework/boot/bind/PropertiesConfigurationFactoryTests.java b/spring-boot/src/test/java/org/springframework/boot/bind/PropertiesConfigurationFactoryTests.java
index 99b4f59cb5..c568e85565 100644
--- a/spring-boot/src/test/java/org/springframework/boot/bind/PropertiesConfigurationFactoryTests.java
+++ b/spring-boot/src/test/java/org/springframework/boot/bind/PropertiesConfigurationFactoryTests.java
@@ -139,6 +139,8 @@ public class PropertiesConfigurationFactoryTests {
 
 		private String spring_foo_baz;
 
+		private String fooBar;
+
 		public String getSpringFooBaz() {
 			return this.spring_foo_baz;
 		}
@@ -163,6 +165,14 @@ public class PropertiesConfigurationFactoryTests {
 			this.bar = bar;
 		}
 
+		public String getFooBar() {
+			return this.fooBar;
+		}
+
+		public void setFooBar(String fooBar) {
+			this.fooBar = fooBar;
+		}
+
 	}
 
 }
diff --git a/spring-boot/src/test/java/org/springframework/boot/bind/RelaxedDataBinderTests.java b/spring-boot/src/test/java/org/springframework/boot/bind/RelaxedDataBinderTests.java
index 8a9d0f578d..484043e273 100644
--- a/spring-boot/src/test/java/org/springframework/boot/bind/RelaxedDataBinderTests.java
+++ b/spring-boot/src/test/java/org/springframework/boot/bind/RelaxedDataBinderTests.java
@@ -525,6 +525,18 @@ public class RelaxedDataBinderTests {
 		assertThat(target.getFoo(), equalTo("b"));
 	}
 
+	@Test
+	public void testMixed() throws Exception {
+		// gh-3385
+		VanillaTarget target = new VanillaTarget();
+		RelaxedDataBinder binder = getBinder(target, "test");
+		MutablePropertyValues values = new MutablePropertyValues();
+		values.add("test.FOO_BAZ", "boo");
+		values.add("test.foo-baz", "bar");
+		binder.bind(values);
+		assertEquals("boo", target.getFooBaz());
+	}
+
 	private void doTestBindCaseInsensitiveEnums(VanillaTarget target) throws Exception {
 		BindingResult result = bind(target, "bingo: THIS");
 		assertThat(result.getErrorCount(), equalTo(0));
@@ -555,16 +567,6 @@ public class RelaxedDataBinderTests {
 		return bind(target, values, null);
 	}
 
-	private BindingResult bind(DataBinder binder, Object target, String values)
-			throws Exception {
-		Properties properties = PropertiesLoaderUtils
-				.loadProperties(new ByteArrayResource(values.getBytes()));
-		binder.bind(new MutablePropertyValues(properties));
-		binder.validate();
-
-		return binder.getBindingResult();
-	}
-
 	private BindingResult bind(Object target, String values, String namePrefix)
 			throws Exception {
 		return bind(getBinder(target, namePrefix), target, values);
@@ -580,6 +582,16 @@ public class RelaxedDataBinderTests {
 		return binder;
 	}
 
+	private BindingResult bind(DataBinder binder, Object target, String values)
+			throws Exception {
+		Properties properties = PropertiesLoaderUtils
+				.loadProperties(new ByteArrayResource(values.getBytes()));
+		binder.bind(new MutablePropertyValues(properties));
+		binder.validate();
+
+		return binder.getBindingResult();
+	}
+
 	@Documented
 	@Target({ ElementType.FIELD })
 	@Retention(RUNTIME)
diff --git a/spring-boot/src/test/java/org/springframework/boot/context/properties/ConfigurationPropertiesBindingPostProcessorTests.java b/spring-boot/src/test/java/org/springframework/boot/context/properties/ConfigurationPropertiesBindingPostProcessorTests.java
index 4ff888b3d3..37b97a963c 100644
--- a/spring-boot/src/test/java/org/springframework/boot/context/properties/ConfigurationPropertiesBindingPostProcessorTests.java
+++ b/spring-boot/src/test/java/org/springframework/boot/context/properties/ConfigurationPropertiesBindingPostProcessorTests.java
@@ -236,6 +236,29 @@ public class ConfigurationPropertiesBindingPostProcessorTests {
 		this.context.refresh();
 	}
 
+	@Test
+	public void relaxedPropertyNamesSame() throws Exception {
+		this.context = new AnnotationConfigApplicationContext();
+		EnvironmentTestUtils.addEnvironment(this.context, "test.FOO_BAR:test1");
+		EnvironmentTestUtils.addEnvironment(this.context, "test.FOO_BAR:test2");
+		this.context.register(RelaxedPropertyNames.class);
+		this.context.refresh();
+		assertThat(this.context.getBean(RelaxedPropertyNames.class).getFooBar(),
+				equalTo("test2"));
+	}
+
+	@Test
+	public void relaxedPropertyNamesMixed() throws Exception {
+		// gh-3385
+		this.context = new AnnotationConfigApplicationContext();
+		EnvironmentTestUtils.addEnvironment(this.context, "test.foo-bar:test1");
+		EnvironmentTestUtils.addEnvironment(this.context, "test.FOO_BAR:test2");
+		this.context.register(RelaxedPropertyNames.class);
+		this.context.refresh();
+		assertThat(this.context.getBean(RelaxedPropertyNames.class).getFooBar(),
+				equalTo("test2"));
+	}
+
 	@Configuration
 	@EnableConfigurationProperties
 	public static class TestConfigurationWithValidatingSetter {
@@ -468,6 +491,23 @@ public class ConfigurationPropertiesBindingPostProcessorTests {
 
 	}
 
+	@Configuration
+	@EnableConfigurationProperties
+	@ConfigurationProperties(prefix = "test")
+	public static class RelaxedPropertyNames {
+
+		private String fooBar;
+
+		public String getFooBar() {
+			return this.fooBar;
+		}
+
+		public void setFooBar(String fooBar) {
+			this.fooBar = fooBar;
+		}
+
+	}
+
 	@SuppressWarnings("rawtypes")
 	// Must be a raw type
 	static class FactoryBeanTester implements FactoryBean, InitializingBean {