diff --git a/apps/openmw/mwgui/spellbuyingwindow.cpp b/apps/openmw/mwgui/spellbuyingwindow.cpp
index a66b21ba2b..2a67af5498 100644
--- a/apps/openmw/mwgui/spellbuyingwindow.cpp
+++ b/apps/openmw/mwgui/spellbuyingwindow.cpp
@@ -19,6 +19,7 @@
 #include "../mwmechanics/actorutil.hpp"
 #include "../mwmechanics/creaturestats.hpp"
 #include "../mwmechanics/spells.hpp"
+#include "../mwmechanics/spellutil.hpp"
 
 namespace MWGui
 {
@@ -43,8 +44,8 @@ namespace MWGui
         const MWWorld::ESMStore& store = *MWBase::Environment::get().getESMStore();
 
         int price = std::max(1,
-            static_cast<int>(
-                spell.mData.mCost * store.get<ESM::GameSetting>().find("fSpellValueMult")->mValue.getFloat()));
+            static_cast<int>(MWMechanics::calcSpellCost(spell)
+                * store.get<ESM::GameSetting>().find("fSpellValueMult")->mValue.getFloat()));
         price = MWBase::Environment::get().getMechanicsManager()->getBarterOffer(mPtr, price, true);
 
         MWWorld::Ptr player = MWMechanics::getPlayer();