diff --git a/apps/openmw/mwphysics/physicssystem.cpp b/apps/openmw/mwphysics/physicssystem.cpp
index f97c5fd13..c7df22aef 100644
--- a/apps/openmw/mwphysics/physicssystem.cpp
+++ b/apps/openmw/mwphysics/physicssystem.cpp
@@ -288,7 +288,7 @@ namespace MWPhysics
             if (MWBase::Environment::get().getWorld()->isInStorm())
             {
                 osg::Vec3f stormDirection = MWBase::Environment::get().getWorld()->getStormDirection();
-                float angleDegrees = osg::RadiansToDegrees(std::acos(stormDirection * velocity));
+                float angleDegrees = osg::RadiansToDegrees(std::acos(stormDirection * velocity / (stormDirection.length() * velocity.length())));
                 static const float fStromWalkMult = MWBase::Environment::get().getWorld()->getStore().get<ESM::GameSetting>()
                         .find("fStromWalkMult")->getFloat();
                 velocity *= 1.f-(fStromWalkMult * (angleDegrees/180.f));