diff --git a/apps/openmw/mwmechanics/spells.hpp b/apps/openmw/mwmechanics/spells.hpp
index 7caeba6e8c..ab799ffe12 100644
--- a/apps/openmw/mwmechanics/spells.hpp
+++ b/apps/openmw/mwmechanics/spells.hpp
@@ -74,7 +74,7 @@ namespace MWMechanics
 
             TIterator end() const;
 
-            bool hasSpell(const std::string& spell) { return mSpells.find(Misc::StringUtils::lowerCase(spell)) != mSpells.end(); }
+            bool hasSpell(const std::string& spell) const { return mSpells.find(Misc::StringUtils::lowerCase(spell)) != mSpells.end(); }
 
             void add (const std::string& spell);
             ///< Adding a spell that is already listed in *this is a no-op.