diff --git a/services/clsi/app/js/CompileController.js b/services/clsi/app/js/CompileController.js
index dcf56d695b..a5dc885da0 100644
--- a/services/clsi/app/js/CompileController.js
+++ b/services/clsi/app/js/CompileController.js
@@ -125,7 +125,7 @@ module.exports = CompileController = {
                   outputFiles: outputFiles.map(file => {
                     return {
                       url:
-                        `${Settings.apis.clsi.url}/project/${request.project_id}` +
+                        `${Settings.apis.clsi.outputUrl}/project/${request.project_id}` +
                         (request.user_id != null
                           ? `/user/${request.user_id}`
                           : '') +
diff --git a/services/clsi/config/settings.defaults.js b/services/clsi/config/settings.defaults.js
index b724bb5493..9a86dd36dd 100644
--- a/services/clsi/config/settings.defaults.js
+++ b/services/clsi/config/settings.defaults.js
@@ -34,7 +34,12 @@ module.exports = {
   },
   apis: {
     clsi: {
+      // Internal requests (used by tests only at the time of writing).
       url: `http://${process.env.CLSI_HOST || 'localhost'}:3013`,
+      // External url prefix for output files, e.g. for requests via load-balancers.
+      outputUrl: `http://${process.env.CLSI_HOST || 'localhost'}:3013${
+        process.env.ZONE ? `/zone/${process.env.ZONE}` : ''
+      }`,
     },
     clsiPerf: {
       host: `${process.env.CLSI_PERF_HOST || 'localhost'}:${
diff --git a/services/clsi/test/unit/js/CompileControllerTests.js b/services/clsi/test/unit/js/CompileControllerTests.js
index 792c7adc7e..8d66948b1f 100644
--- a/services/clsi/test/unit/js/CompileControllerTests.js
+++ b/services/clsi/test/unit/js/CompileControllerTests.js
@@ -69,7 +69,7 @@ describe('CompileController', function () {
         '@overleaf/settings': (this.Settings = {
           apis: {
             clsi: {
-              url: 'http://clsi.example.com',
+              outputUrl: 'http://clsi.example.com',
             },
           },
         }),
@@ -157,7 +157,7 @@ describe('CompileController', function () {
               timings: this.timings,
               outputFiles: this.output_files.map(file => {
                 return {
-                  url: `${this.Settings.apis.clsi.url}/project/${this.project_id}/build/${file.build}/output/${file.path}`,
+                  url: `${this.Settings.apis.clsi.outputUrl}/project/${this.project_id}/build/${file.build}/output/${file.path}`,
                   ...file,
                 }
               }),
@@ -198,7 +198,7 @@ describe('CompileController', function () {
               timings: this.timings,
               outputFiles: this.output_files.map(file => {
                 return {
-                  url: `${this.Settings.apis.clsi.url}/project/${this.project_id}/build/${file.build}/output/${file.path}`,
+                  url: `${this.Settings.apis.clsi.outputUrl}/project/${this.project_id}/build/${file.build}/output/${file.path}`,
                   ...file,
                 }
               }),
@@ -240,7 +240,7 @@ describe('CompileController', function () {
               timings: this.timings,
               outputFiles: this.output_files.map(file => {
                 return {
-                  url: `${this.Settings.apis.clsi.url}/project/${this.project_id}/build/${file.build}/output/${file.path}`,
+                  url: `${this.Settings.apis.clsi.outputUrl}/project/${this.project_id}/build/${file.build}/output/${file.path}`,
                   ...file,
                 }
               }),