diff --git a/docker-java-api/src/main/java/com/github/dockerjava/api/model/ExposedPorts.java b/docker-java-api/src/main/java/com/github/dockerjava/api/model/ExposedPorts.java
index 445cba2de..9fb9910bd 100644
--- a/docker-java-api/src/main/java/com/github/dockerjava/api/model/ExposedPorts.java
+++ b/docker-java-api/src/main/java/com/github/dockerjava/api/model/ExposedPorts.java
@@ -1,14 +1,14 @@
 package com.github.dockerjava.api.model;
 
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonValue;
+
 import java.io.Serializable;
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-import com.fasterxml.jackson.annotation.JsonCreator;
-import com.fasterxml.jackson.annotation.JsonValue;
-
 public class ExposedPorts implements Serializable {
     private static final long serialVersionUID = 1L;
 
@@ -36,8 +36,9 @@ public static ExposedPorts fromPrimitive(Map<String, Object> object) {
     @JsonValue
     public Map<String, Object> toPrimitive() {
         return Stream.of(exposedPorts).collect(Collectors.toMap(
-                ExposedPort::toString,
-                __ -> new Object()
+            ExposedPort::toString,
+            __ -> new Object(),
+            (a, b) -> a
         ));
     }
 
diff --git a/docker-java/src/test/java/com/github/dockerjava/api/model/ExposedPortsTest.java b/docker-java/src/test/java/com/github/dockerjava/api/model/ExposedPortsTest.java
index c64d5ace2..456e65ca4 100644
--- a/docker-java/src/test/java/com/github/dockerjava/api/model/ExposedPortsTest.java
+++ b/docker-java/src/test/java/com/github/dockerjava/api/model/ExposedPortsTest.java
@@ -6,10 +6,13 @@
 import org.junit.Test;
 
 import java.util.List;
+import java.util.Map;
 import java.util.Map.Entry;
 
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.aMapWithSize;
 import static org.hamcrest.Matchers.arrayContainingInAnyOrder;
+import static org.hamcrest.Matchers.arrayWithSize;
 import static org.hamcrest.Matchers.notNullValue;
 
 public class ExposedPortsTest {
@@ -46,4 +49,19 @@ public void usesFromJson() throws Exception {
             new ExposedPort(3868, InternetProtocol.SCTP)
         ));
     }
+
+    @Test
+    public void usesFromJsonWithDuplicate() throws Exception {
+        ExposedPorts ports = new ExposedPorts(
+            new ExposedPort(80, InternetProtocol.UDP),
+            new ExposedPort(80),
+            new ExposedPort(80)
+        );
+
+        assertThat(ports, notNullValue());
+        assertThat(ports.getExposedPorts(), arrayWithSize(3));
+
+        Map<String, Object> map = ports.toPrimitive();
+        assertThat(map, aMapWithSize(2));
+    }
 }