diff --git a/config.js b/config.js
index c63fdd6..cb38e43 100644
--- a/config.js
+++ b/config.js
@@ -117,7 +117,7 @@ config.maxConcurrency = parseInt(argv.max_concurrency || fromConfigFile("maxConc
 config.maxRuntime = parseInt(argv.max_runtime || fromConfigFile("maxRuntime", -1));
 
 // Detect 7z availability
-// const childProcess = spawnSync("7z", ['--help']);
-config.has7z = false; //childProcess.status === 0;
+const childProcess = spawnSync("7z", ['--help']);
+config.has7z = childProcess.status === 0;
 
 module.exports = config;
diff --git a/index.js b/index.js
index 1ad191e..9808739 100644
--- a/index.js
+++ b/index.js
@@ -901,9 +901,9 @@ if (config.test) {
     if (config.testDropUploads) logger.info("Uploads will drop at random");
 }
 
-// if (!config.has7z){
-//     logger.warn("The 7z program is not installed, falling back to legacy (zipping will be slower)");
-// }
+if (!config.has7z){
+    logger.warn("The 7z program is not installed, falling back to legacy (zipping will be slower)");
+}
 
 let commands = [
     cb => odmInfo.initialize(cb),
diff --git a/libs/processRunner.js b/libs/processRunner.js
index f6b0ab0..f5e000c 100644
--- a/libs/processRunner.js
+++ b/libs/processRunner.js
@@ -76,6 +76,9 @@ function makeRunner(command, args, requiredOptions = [], outputTestFile = null,
         if (outputReceived !== undefined){
             childProcess.stdout.on('data', chunk => outputReceived(chunk.toString()));
             childProcess.stderr.on('data', chunk => outputReceived(chunk.toString()));
+        }else{
+            childProcess.stdout.on('data', () => {});
+            childProcess.stderr.on('data', () => {});
         }
 
         return childProcess;
@@ -90,7 +93,7 @@ module.exports = {
                      ["projectFolderPath"]),
 
     sevenZip: makeRunner("7z", function(options){
-            return ["a", "-r", "-bd", options.destination].concat(options.pathsToArchive);
+            return ["a", "-mx=0", "-r", "-bd", options.destination].concat(options.pathsToArchive);
         },
         ["destination", "pathsToArchive", "cwd"],
         null,