diff --git a/app/controllers/api/orders_controller.rb b/app/controllers/api/orders_controller.rb
index 65176a0008..a0a4a0c013 100644
--- a/app/controllers/api/orders_controller.rb
+++ b/app/controllers/api/orders_controller.rb
@@ -47,7 +47,7 @@ module Api
     private
 
     def payment_capture_failed
-      render json: { error: t(:payment_processing_failed) }, status: :unprocessable_entity
+      render json: { error: I18n.t(:payment_processing_failed) }, status: :unprocessable_entity
     end
 
     def serialized_orders(orders)
diff --git a/spec/controllers/api/orders_controller_spec.rb b/spec/controllers/api/orders_controller_spec.rb
index e93c6d300b..2a5421e9cb 100644
--- a/spec/controllers/api/orders_controller_spec.rb
+++ b/spec/controllers/api/orders_controller_spec.rb
@@ -285,6 +285,18 @@ module Api
           expect(order.reload.pending_payments.empty?).to be true
           expect_order
         end
+
+        context "when payment is not required" do
+          before do
+            allow_any_instance_of(Spree::Order).to receive(:payment_required?) { false }
+          end
+
+          it "returns an error" do
+            put :capture, params: { id: order.number }
+
+            expect(json_response['error']).to eq I18n.t(:payment_processing_failed)
+          end
+        end
       end
 
       describe "#ship" do