diff --git a/database/migrations/2016_11_03_113316_add_invoice_signature.php b/database/migrations/2016_11_03_113316_add_invoice_signature.php
index 5a567dcf1129..34e42552741e 100644
--- a/database/migrations/2016_11_03_113316_add_invoice_signature.php
+++ b/database/migrations/2016_11_03_113316_add_invoice_signature.php
@@ -12,40 +12,44 @@ class AddInvoiceSignature extends Migration
      */
     public function up()
     {
-        Schema::table('invitations', function($table)
+        if ( ! Schema::hasColumn('invitations', 'signature_base64'))
         {
-            $table->text('signature_base64')->nullable();
-            $table->timestamp('signature_date')->nullable();
-        });
+            Schema::table('invitations', function($table)
+            {
+                $table->text('signature_base64')->nullable();
+                $table->timestamp('signature_date')->nullable();
+            });
 
-        Schema::table('companies', function($table)
-        {
-            $table->string('utm_source')->nullable();
-            $table->string('utm_medium')->nullable();
-            $table->string('utm_campaign')->nullable();
-            $table->string('utm_term')->nullable();
-            $table->string('utm_content')->nullable();
-        });
+            Schema::table('companies', function($table)
+            {
+                $table->string('utm_source')->nullable();
+                $table->string('utm_medium')->nullable();
+                $table->string('utm_campaign')->nullable();
+                $table->string('utm_term')->nullable();
+                $table->string('utm_content')->nullable();
+            });
 
-        Schema::table('payment_methods', function($table)
-        {
-            $table->dropForeign('payment_methods_account_gateway_token_id_foreign');
-        });
+            Schema::table('payment_methods', function($table)
+            {
+                $table->unsignedInteger('account_gateway_token_id')->nullable()->change();
+                $table->dropForeign('payment_methods_account_gateway_token_id_foreign');
+            });
 
-        Schema::table('payment_methods', function($table)
-        {
-            $table->foreign('account_gateway_token_id')->references('id')->on('account_gateway_tokens')->onDelete('cascade');
-        });
+            Schema::table('payment_methods', function($table)
+            {
+                $table->foreign('account_gateway_token_id')->references('id')->on('account_gateway_tokens')->onDelete('cascade');
+            });
 
-        Schema::table('payments', function($table)
-        {
-            $table->dropForeign('payments_payment_method_id_foreign');
-        });
+            Schema::table('payments', function($table)
+            {
+                $table->dropForeign('payments_payment_method_id_foreign');
+            });
 
-        Schema::table('payments', function($table)
-        {
-            $table->foreign('payment_method_id')->references('id')->on('payment_methods')->onDelete('cascade');;
-        });
+            Schema::table('payments', function($table)
+            {
+                $table->foreign('payment_method_id')->references('id')->on('payment_methods')->onDelete('cascade');;
+            });
+        }
     }
 
     /**