diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/filters/TimestampResponseFilter.java b/service/src/main/java/org/whispersystems/textsecuregcm/filters/TimestampResponseFilter.java
index cdf451b4f..5315f6d05 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/filters/TimestampResponseFilter.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/filters/TimestampResponseFilter.java
@@ -5,7 +5,6 @@ import org.whispersystems.textsecuregcm.util.TimestampHeaderUtil;
 import javax.ws.rs.container.ContainerRequestContext;
 import javax.ws.rs.container.ContainerResponseContext;
 import javax.ws.rs.container.ContainerResponseFilter;
-import java.util.Collections;
 
 /**
  * Injects a timestamp header into all outbound responses.
@@ -14,6 +13,6 @@ public class TimestampResponseFilter implements ContainerResponseFilter {
 
     @Override
     public void filter(final ContainerRequestContext requestContext, final ContainerResponseContext responseContext) {
-        responseContext.getStringHeaders().put(TimestampHeaderUtil.TIMESTAMP_HEADER, Collections.singletonList(String.valueOf(System.currentTimeMillis())));
+        responseContext.getHeaders().add(TimestampHeaderUtil.TIMESTAMP_HEADER, System.currentTimeMillis());
     }
 }
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/filters/TimestampResponseFilterTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/filters/TimestampResponseFilterTest.java
new file mode 100644
index 000000000..e5f4d2953
--- /dev/null
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/filters/TimestampResponseFilterTest.java
@@ -0,0 +1,31 @@
+package org.whispersystems.textsecuregcm.filters;
+
+import org.glassfish.jersey.message.internal.HeaderUtils;
+import org.junit.Test;
+import org.whispersystems.textsecuregcm.util.TimestampHeaderUtil;
+
+import javax.ws.rs.container.ContainerRequestContext;
+import javax.ws.rs.container.ContainerResponseContext;
+import javax.ws.rs.core.MultivaluedHashMap;
+import javax.ws.rs.core.MultivaluedMap;
+
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class TimestampResponseFilterTest {
+
+    @Test
+    public void testFilter() {
+        final ContainerRequestContext        requestContext  = mock(ContainerRequestContext.class);
+        final ContainerResponseContext       responseContext = mock(ContainerResponseContext.class);
+
+        final MultivaluedMap<String, Object> headers         = HeaderUtils.createOutbound();
+
+        when(responseContext.getHeaders()).thenReturn(headers);
+
+        new TimestampResponseFilter().filter(requestContext, responseContext);
+
+        assertTrue(headers.containsKey(TimestampHeaderUtil.TIMESTAMP_HEADER));
+    }
+}