diff --git a/app/DoctrineMigrations/Version20170719231144.php b/app/DoctrineMigrations/Version20170719231144.php
index 0c7491507..9a6f3e938 100644
--- a/app/DoctrineMigrations/Version20170719231144.php
+++ b/app/DoctrineMigrations/Version20170719231144.php
@@ -31,7 +31,7 @@ class Version20170719231144 extends AbstractMigration implements ContainerAwareI
 
         // Find tags which need to be merged
         $dupTags = $this->connection->query('
-            SELECT LOWER(label)
+            SELECT LOWER(label) AS lower_label
             FROM   ' . $this->getTable('tag') . '
             GROUP BY LOWER(label)
             HAVING COUNT(*) > 1'
@@ -39,16 +39,18 @@ class Version20170719231144 extends AbstractMigration implements ContainerAwareI
         $dupTags->execute();
 
         foreach ($dupTags->fetchAll() as $duplicates) {
-            $label = $duplicates['LOWER(label)'];
+            $label = $duplicates['lower_label'];
 
             // Retrieve all duplicate tags for a given tag
-            $tags = $this->connection->query('
+            $tags = $this->connection->executeQuery('
                 SELECT id
-                FROM   ' . $this->getTable('tag') . "
-                WHERE  LOWER(label) = '" . $label . "'
-                ORDER BY id ASC"
+                FROM   ' . $this->getTable('tag') . '
+                WHERE  LOWER(label) = :label
+                ORDER BY id ASC',
+                [
+                  'label' => $label,
+                ]
             );
-            $tags->execute();
 
             $first = true;
             $newId = null;
@@ -70,7 +72,18 @@ class Version20170719231144 extends AbstractMigration implements ContainerAwareI
                 $this->addSql('
                     UPDATE ' . $this->getTable('entry_tag') . '
                     SET    tag_id = ' . $newId . '
-                    WHERE  tag_id IN (' . implode(',', $ids) . ')'
+                    WHERE  tag_id IN (' . implode(',', $ids) . ')
+                        AND entry_id NOT IN (
+                           SELECT entry_id
+                           FROM ' . $this->getTable('entry_tag') . '
+                           WHERE tag_id = ' . $newId . '
+                        )'
+                );
+
+                // Delete links to unused tags
+                $this->addSql('
+                    DELETE FROM ' . $this->getTable('entry_tag') . '
+                    WHERE tag_id IN (' . implode(',', $ids) . ')'
                 );
 
                 // Delete unused tags