diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index ae3c5c2..ea70633 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -2607,7 +2607,7 @@ function drupal_fast_404() {
  */
 function drupal_installation_attempted() {
   // This cannot rely on the MAINTENANCE_MODE constant, since that would prevent
-  // tests from using the non-interactive installer, in which case Drupal is
+  // tests from using the non-interactive installer, in which case Drupal
   // only happens to be installed within the same request, but subsequently
   // executed code does not involve the installer at all.
   // @see install_drupal()
diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 2407d51..c14155d 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -100,7 +100,9 @@ function install_drupal($settings = array()) {
   // reliably check whether it is running during the installer.
   // @see drupal_installation_attempted()
   $state = $install_state;
-  unset($install_state);
+  if (!empty($install_state['installation_finished'])) {
+    unset($install_state);
+  }
 
   // All available tasks for this page request are now complete. Interactive
   // installations can send output to the browser or redirect the user to the