diff --git a/src/DrupalCI/Plugin/BuildSteps/generic/Composer.php b/src/DrupalCI/Plugin/BuildSteps/generic/Composer.php
new file mode 100644
index 0000000..fefc0f1
--- /dev/null
+++ b/src/DrupalCI/Plugin/BuildSteps/generic/Composer.php
@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * @file
+ * Contains \DrupalCI\Plugin\BuildSteps\setup\Composer
+ */
+
+namespace DrupalCI\Plugin\BuildSteps\generic;
+
+use DrupalCI\Plugin\BuildSteps\setup\SetupBase;
+use DrupalCI\Plugin\JobTypes\JobInterface;
+use DrupalCI\Console\Output;
+
+/**
+ * @PluginID("composer")
+ *
+ * Processes "setup: composer:" instructions from within a job
+ * definition.
+ */
+class Composer extends SetupBase {
+
+  /**
+   * {@inheritdoc}
+   *
+   * @param string|array $arguments
+   *   Arguments for a composer command. May be a string if one composer command
+   *   is required to run or an array if multiple commands should run.
+   */
+  public function run(JobInterface $job, $data) {
+    // Normalize the arguments to an array format.
+    $data_list = (array) $data;
+
+    $workingdir = $job->getJobCodebase()->getWorkingDir();
+
+    foreach ($data_list as $data) {
+      $cmd = $this->buildComposerCommand($data, $workingdir);
+      $this->exec($cmd, $cmdoutput, $result);
+    }
+  }
+
+  /**
+   * Returns a full composer command based on the passed-in arguments.
+   *
+   * @param string $arguments
+   *   The arguments for the composer command.
+   *
+   * @return string
+   *   The full composer command string.
+   */
+  protected function buildComposerCommand($data, $workingdir) {
+    return "composer $data $workingdir";
+  }
+
+}
diff --git a/src/DrupalCI/Plugin/BuildSteps/setup/Composer.php b/src/DrupalCI/Plugin/BuildSteps/setup/Composer.php
deleted file mode 100644
index a8463cc..0000000
--- a/src/DrupalCI/Plugin/BuildSteps/setup/Composer.php
+++ /dev/null
@@ -1,53 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \DrupalCI\Plugin\BuildSteps\setup\Composer
- */
-
-namespace DrupalCI\Plugin\BuildSteps\setup;
-
-use DrupalCI\Plugin\JobTypes\JobInterface;
-use DrupalCI\Console\Output;
-
-/**
- * @PluginID("composer")
- *
- * Processes "setup: composer:" instructions from within a job
- * definition.
- */
-class Composer extends SetupBase {
-
-  /**
-   * {@inheritdoc}
-   *
-   * @param string|array $arguments
-   *   Arguments for a composer command. May be a string if one composer command
-   *   is required to run or an array if multiple commands should run.
-   */
-  public function run(JobInterface $job, $data) {
-    // Normalize the arguments to an array format.
-    $data_list = (array) $data;
-
-    $workingdir = $job->getJobCodebase()->getWorkingDir();
-
-    foreach ($data_list as $data) {
-      $cmd = $this->buildComposerCommand($data, $workingdir);
-      $this->exec($cmd, $cmdoutput, $result);
-    }
-  }
-
-  /**
-   * Returns a full composer command based on the passed-in arguments.
-   *
-   * @param string $arguments
-   *   The arguments for the composer command.
-   *
-   * @return string
-   *   The full composer command string.
-   */
-  protected function buildComposerCommand($data, $workingdir) {
-    return "composer $data $workingdir";
-  }
-
-}
diff --git a/src/DrupalCI/Plugin/Preprocess/definition/ComposerInstall.php b/src/DrupalCI/Plugin/Preprocess/definition/ComposerInstall.php
index 999c056..43d62b0 100644
--- a/src/DrupalCI/Plugin/Preprocess/definition/ComposerInstall.php
+++ b/src/DrupalCI/Plugin/Preprocess/definition/ComposerInstall.php
@@ -43,6 +43,28 @@ class ComposerInstall {
       $definition['setup']['composer'] = [];
     }
 
-    $definition['setup']['composer'][] = "install --prefer-dist --working-dir ";
+    $definition['setup']['composer'][] = 'install --prefer-dist --working-dir ';
+
+    // Run additional composer steps for contrib modules.
+    if ($this->hasComposerDependencies($definition)) {
+      $definition['setup']['composer'][] = 'config repositories.drupal composer https://packagist.drupal-composer.org --working-dir ';
+      $definition['setup']['composer'][] = 'require mile23/drupal-merge-plugin --working-dir ';
+      $definition['setup']['composer'][] = 'update --working-dir ';
+    }
+  }
+
+  /**
+   * Check to see if additional repositories make use of composer.
+   *
+   * This will return TRUE for all cases where an additional repository is
+   * defined in the job because at this point the job is being preprocessed,
+   * and no files have been downloaded yet.
+   *
+   * @param array $definition
+   *   The job definition array.
+   * @return boolean
+   */
+  protected function hasComposerDependencies(array $definition) {
+    return count($definition['setup']['checkout']) > 1;
   }
 }