diff --git a/apps/openmw/mwmechanics/aipackage.cpp b/apps/openmw/mwmechanics/aipackage.cpp
index 8dcf37355..204cf2f3f 100644
--- a/apps/openmw/mwmechanics/aipackage.cpp
+++ b/apps/openmw/mwmechanics/aipackage.cpp
@@ -25,6 +25,14 @@
 
 #include <osg/Quat>
 
+namespace
+{
+    float divOrMax(float dividend, float divisor)
+    {
+        return divisor == 0 ? std::numeric_limits<float>::max() * std::numeric_limits<float>::epsilon() : dividend / divisor;
+    }
+}
+
 MWMechanics::AiPackage::AiPackage(AiPackageTypeId typeId, const Options& options) :
     mTypeId(typeId),
     mOptions(options),
@@ -416,14 +424,15 @@ DetourNavigator::Flags MWMechanics::AiPackage::getNavigatorFlags(const MWWorld::
     const MWWorld::Class& actorClass = actor.getClass();
     DetourNavigator::Flags result = DetourNavigator::Flag_none;
 
-    if (actorClass.isPureWaterCreature(actor)
-        || (getTypeId() != AiPackageTypeId::Wander
-            && ((allowToFollowOverWaterSurface && getTypeId() == AiPackageTypeId::Follow)
-                || actorClass.canSwim(actor)
-                || hasWaterWalking(actor))))
+    if ((actorClass.isPureWaterCreature(actor)
+         || (getTypeId() != AiPackageTypeId::Wander
+             && ((allowToFollowOverWaterSurface && getTypeId() == AiPackageTypeId::Follow)
+                 || actorClass.canSwim(actor)
+                 || hasWaterWalking(actor)))
+        ) && actorClass.getSwimSpeed(actor) > 0)
         result |= DetourNavigator::Flag_swim;
 
-    if (actorClass.canWalk(actor))
+    if (actorClass.canWalk(actor) && actor.getClass().getWalkSpeed(actor) > 0)
         result |= DetourNavigator::Flag_walk;
 
     if (actorClass.isBipedal(actor) && getTypeId() != AiPackageTypeId::Wander)
@@ -439,15 +448,15 @@ DetourNavigator::AreaCosts MWMechanics::AiPackage::getAreaCosts(const MWWorld::P
     const MWWorld::Class& actorClass = actor.getClass();
 
     if (flags & DetourNavigator::Flag_swim)
-        costs.mWater = costs.mWater / actorClass.getSwimSpeed(actor);
+        costs.mWater = divOrMax(costs.mWater, actorClass.getSwimSpeed(actor));
 
     if (flags & DetourNavigator::Flag_walk)
     {
         float walkCost;
         if (getTypeId() == AiPackageTypeId::Wander)
-            walkCost = 1.0 / actorClass.getWalkSpeed(actor);
+            walkCost = divOrMax(1.0, actorClass.getWalkSpeed(actor));
         else
-            walkCost = 1.0 / actorClass.getRunSpeed(actor);
+            walkCost = divOrMax(1.0, actorClass.getRunSpeed(actor));
         costs.mDoor = costs.mDoor * walkCost;
         costs.mPathgrid = costs.mPathgrid * walkCost;
         costs.mGround = costs.mGround * walkCost;