diff -u b/core/lib/Drupal/Core/Extension/ModuleInstaller.php b/core/lib/Drupal/Core/Extension/ModuleInstaller.php
--- b/core/lib/Drupal/Core/Extension/ModuleInstaller.php
+++ b/core/lib/Drupal/Core/Extension/ModuleInstaller.php
@@ -266,16 +266,4 @@
         $this->configInstaller->checkConfigurationToInstall('module', $module);
 
-        // Install profiles can not have config clashes. Configuration that
-        // has the same name as a module's configuration will be used instead.
-        if ($module != drupal_get_profile()) {
-          // Validate default configuration of this module. Bail if unable to
-          // install. Should not continue installing more modules because those
-          // may depend on this one.
-          $existing_configuration = $this->configInstaller->findPreExistingConfiguration('module', $module);
-          if (!empty($existing_configuration)) {
-            throw PreExistingConfigException::create($module, $existing_configuration);
-          }
-        }
-
         // Save this data without checking schema. This is a performance
         // improvement for module installation.
@@ -364,12 +352,6 @@
             ->setSyncing(TRUE)
             ->setSourceStorage($source_storage);
         }
-        else {
-          // If we're not in a config synchronization reset the source storage
-          // so that the extension install storage will pick up the new
-          // configuration.
-          $this->configInstaller->resetSourceStorage();
-        }
         $this->configInstaller->installDefaultConfig('module', $module);
 
         // If the module has no current updates, but has some that were