diff --git a/metatag.install b/metatag.install
index 6ff3292..31af61a 100644
--- a/metatag.install
+++ b/metatag.install
@@ -230,14 +230,33 @@ function metatag_update_7001() {
   );
   $keys = array('primary key' => array($field_name));
 
-  // Before making any changes, drop the existing primary key. Unforunately
-  // there is no API way to check if a primary key exists, so if it doesn't
-  // exist the db_drop_primary_key() call will fail.
-  try {
-    db_drop_primary_key($table_name);
+  // Before making any changes, drop the existing primary key. This is a little
+  // hackish as there's no Drupal API to identify whether a table already has a
+  // primary key.
+  $db_class = get_class(db_query("SELECT entity_id FROM {metatag}"));
+  // MySQL.
+  if ($db_class == 'DatabaseConnection_mysql') {
+    $indices = db_query("SHOW indexes FROM {metatag_config} WHERE key_name = 'PRIMARY'");
+  }
+  // PostgreSQL.
+  elseif ($db_class == 'DatabaseConnection_pgsql') {
+    $indices = db_query("SELECT c.column_name, c.data_type
+      FROM information_schema.table_constraints tc 
+        JOIN information_schema.constraint_column_usage AS ccu
+          USING (constraint_schema, constraint_name) 
+        JOIN information_schema.columns AS c
+          ON c.table_schema = tc.constraint_schema AND tc.table_name = c.table_name AND ccu.column_name = c.column_name
+      WHERE constraint_type = 'PRIMARY KEY' and tc.table_name = {metatag_config}");
+  }
+  // A different database. Hopefully no sites were using the original Metatags
+  // module on something other than MySQL or PostgreSQL.
+  else {
+    $indices = NULL;
   }
-  catch (Exception $e) {
-    drupal_set_message('Caught an exception: ', $e->getMessage());
+
+  // If ither the $indices query was not ran
+  if (is_null($indices) || $indices->getCount() > 0) {
+    db_drop_primary_key($table_name);
   }
 
   // Rejig the field, and turn on the primary key again.