diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java b/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java
index 050291102..0c7e75f82 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java
@@ -73,6 +73,7 @@ import org.whispersystems.textsecuregcm.controllers.SecureBackupController;
 import org.whispersystems.textsecuregcm.controllers.SecureStorageController;
 import org.whispersystems.textsecuregcm.controllers.StickerController;
 import org.whispersystems.textsecuregcm.controllers.VoiceVerificationController;
+import org.whispersystems.textsecuregcm.filters.TimestampResponseFilter;
 import org.whispersystems.textsecuregcm.limits.RateLimiters;
 import org.whispersystems.textsecuregcm.liquibase.NameableMigrationsBundle;
 import org.whispersystems.textsecuregcm.mappers.DeviceLimitExceededExceptionMapper;
@@ -323,6 +324,8 @@ public class WhisperServerService extends Application<WhisperServerConfiguration
                                                                                       DisabledPermittedAccount.class, disabledPermittedAccountAuthFilter)));
     environment.jersey().register(new PolymorphicAuthValueFactoryProvider.Binder<>(ImmutableSet.of(Account.class, DisabledPermittedAccount.class)));
 
+    environment.jersey().register(new TimestampResponseFilter());
+
     environment.jersey().register(new AccountController(pendingAccountsManager, accountsManager, usernamesManager, abusiveHostRules, rateLimiters, smsSender, directoryQueue, messagesManager, turnTokenGenerator, config.getTestDevices(), recaptchaClient, gcmSender, apnSender, backupCredentialsGenerator));
     environment.jersey().register(new DeviceController(pendingDevicesManager, accountsManager, messagesManager, directoryQueue, rateLimiters, config.getMaxDevices()));
     environment.jersey().register(new DirectoryController(rateLimiters, directory, directoryCredentialsGenerator));
diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/filters/TimestampResponseFilter.java b/service/src/main/java/org/whispersystems/textsecuregcm/filters/TimestampResponseFilter.java
new file mode 100644
index 000000000..130787a24
--- /dev/null
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/filters/TimestampResponseFilter.java
@@ -0,0 +1,19 @@
+package org.whispersystems.textsecuregcm.filters;
+
+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.
+ */
+public class TimestampResponseFilter implements ContainerResponseFilter {
+
+    private static final String TIMESTAMP_HEADER = "X-Signal-Timestamp";
+
+    @Override
+    public void filter(final ContainerRequestContext requestContext, final ContainerResponseContext responseContext) {
+        responseContext.getStringHeaders().put(TIMESTAMP_HEADER, Collections.singletonList(String.valueOf(System.currentTimeMillis())));
+    }
+}