diff --git a/.travis.yml b/.travis.yml
index fcbb7a998..8e79fbc83 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,9 +8,13 @@ matrix:
       node_js:
         - "10"
 
-      script:
+      install:
         - cd website
         - yarn
+        - cd ..
+
+      script:
+        - cd website
         - yarn build
         - cd ..
 
diff --git a/scripts/yarn-install.js b/scripts/yarn-install.js
index 1157e8128..eb65b8a5e 100644
--- a/scripts/yarn-install.js
+++ b/scripts/yarn-install.js
@@ -22,10 +22,21 @@ Promise.all(
   ),
 )
   .then(async packages => {
-    for (const pkg of packages.reduce((acc, cv) => acc.concat(cv), [])) {
-      const {stderr} = await exec(YARN_PATH, {
-        cwd: pkg.replace('/package.json', ''),
-      });
+    packages = packages.reduce((acc, cv) => acc.concat(cv), []);
+    console.log(`Installing dependencies for ${packages.length} plugins`);
+    for (const pkg of packages) {
+      const {stderr} = await exec(
+        // This script is itself executed by yarn (as postinstall script),
+        // therefore another yarn instance is running, while we are trying to
+        // install the plugin dependencies. We are setting a different port
+        // for the mutex of this yarn instance to make sure, it is not blocked
+        // by the yarn instance which is executing this script. Otherwise this
+        // will cause a deadlock.
+        [YARN_PATH, '--mutex', 'network:30330'].join(' '),
+        {
+          cwd: pkg.replace('/package.json', ''),
+        },
+      );
       if (stderr) {
         console.warn(stderr);
       } else {