diff --git a/classes/TextimageImager.inc b/classes/TextimageImager.inc
index 6094486..734483f 100644
--- a/classes/TextimageImager.inc
+++ b/classes/TextimageImager.inc
@@ -300,20 +300,6 @@ abstract class TextimageImager {
    */
   protected static function buildImage($style, $source, $uri, $extension) {
 
-    // Don't start generating the image if generation is in progress
-    // in another thread.
-    $lock_name = 'textimage_process:' . $uri;
-    if (!file_exists($uri)) {
-      $lock_acquired = lock_acquire($lock_name);
-      if (!$lock_acquired) {
-        return FALSE;
-      }
-    }
-
-    // Reset state.
-    self::setState();
-    self::setState('building_module', 'textimage');
-
     // If no source image specified, we are processing a pure Textimage
     // request. In that case we need to use a dummy 1x1 image stored
     // in textimage/misc/images, and prepend an additional
@@ -333,22 +319,29 @@ abstract class TextimageImager {
       $style['effects'] = $cleanup_effect + $style['effects'];
     }
 
-    // Try to generate the image, unless another thread just did it while we
-    // were acquiring the lock.
-    $success = file_exists($uri) || image_style_create_derivative($style, $source, $uri);
-    if (!$success) {
-      return FALSE;
-    };
-
     // Reset state.
     self::setState();
+    self::setState('building_module', 'textimage');
+
+    // Try a lock to the file generation process. If cannot get the lock,
+    // return success if the file exists already. Otherwise return failure.
+    $lock_name = 'textimage_process:' . $uri;
+    if(!$lock_acquired = lock_acquire($lock_name)) {
+      return file_exists($uri) ? TRUE : FALSE;
+    }
+
+    // Generate the image.
+    $success = image_style_create_derivative($style, $source, $uri);
 
     // Release lock.
     if (!empty($lock_acquired)) {
       lock_release($lock_name);
     }
 
-    return TRUE;
+    // Reset state.
+    self::setState();
+
+    return $success;
   }
 
   /**