diff --git a/apps/openmw/mwclass/npc.cpp b/apps/openmw/mwclass/npc.cpp
index aedac4a37..a29274ca7 100644
--- a/apps/openmw/mwclass/npc.cpp
+++ b/apps/openmw/mwclass/npc.cpp
@@ -302,11 +302,11 @@ namespace MWClass
                 Misc::StringUtils::toLower(faction);
                 if(ref->mBase->mNpdtType != ESM::NPC::NPC_WITH_AUTOCALCULATED_STATS)
                 {
-                    data->mNpcStats.getFactionRanks()[faction] = (int)ref->mBase->mNpdt52.mRank;
+                    data->mNpcStats.setFactionRank(faction, (int)ref->mBase->mNpdt52.mRank);
                 }
                 else
                 {
-                    data->mNpcStats.getFactionRanks()[faction] = (int)ref->mBase->mNpdt12.mRank;
+                    data->mNpcStats.setFactionRank(faction, (int)ref->mBase->mNpdt12.mRank);
                 }
             }
 
diff --git a/apps/openmw/mwdialogue/filter.cpp b/apps/openmw/mwdialogue/filter.cpp
index 2888a6e08..629d99cc2 100644
--- a/apps/openmw/mwdialogue/filter.cpp
+++ b/apps/openmw/mwdialogue/filter.cpp
@@ -68,7 +68,7 @@ bool MWDialogue::Filter::testActor (const ESM::DialInfo& info) const
             return false;
 
         MWMechanics::NpcStats& stats = mActor.getClass().getNpcStats (mActor);
-        std::map<std::string, int>::iterator iter = stats.getFactionRanks().find ( Misc::StringUtils::lowerCase (info.mFaction));
+        std::map<std::string, int>::const_iterator iter = stats.getFactionRanks().find ( Misc::StringUtils::lowerCase (info.mFaction));
 
         if (iter==stats.getFactionRanks().end())
             return false;
@@ -112,7 +112,7 @@ bool MWDialogue::Filter::testPlayer (const ESM::DialInfo& info) const
     if (!info.mPcFaction.empty())
     {
         MWMechanics::NpcStats& stats = player.getClass().getNpcStats (player);
-        std::map<std::string,int>::iterator iter = stats.getFactionRanks().find (Misc::StringUtils::lowerCase (info.mPcFaction));
+        std::map<std::string,int>::const_iterator iter = stats.getFactionRanks().find (Misc::StringUtils::lowerCase (info.mPcFaction));
 
         if(iter==stats.getFactionRanks().end())
             return false;
@@ -379,7 +379,7 @@ int MWDialogue::Filter::getSelectStructInteger (const SelectWrapper& select) con
             if (mActor.getClass().getNpcStats (mActor).getFactionRanks().empty())
                 return 0;
 
-            std::pair<std::string, int> faction =
+            const std::pair<std::string, int> faction =
                 *mActor.getClass().getNpcStats (mActor).getFactionRanks().begin();
 
             int rank = getFactionRank (player, faction.first);
diff --git a/apps/openmw/mwmechanics/npcstats.cpp b/apps/openmw/mwmechanics/npcstats.cpp
index 370c47b1f..13fc14318 100644
--- a/apps/openmw/mwmechanics/npcstats.cpp
+++ b/apps/openmw/mwmechanics/npcstats.cpp
@@ -69,9 +69,41 @@ const std::map<std::string, int>& MWMechanics::NpcStats::getFactionRanks() const
     return mFactionRank;
 }
 
-std::map<std::string, int>& MWMechanics::NpcStats::getFactionRanks()
+void MWMechanics::NpcStats::raiseRank(const std::string &faction)
 {
-    return mFactionRank;
+    const std::string lower = Misc::StringUtils::lowerCase(faction);
+    std::map<std::string, int>::iterator it = mFactionRank.find(lower);
+    if (it != mFactionRank.end())
+    {
+        // Does the next rank exist?
+        const ESM::Faction* faction = MWBase::Environment::get().getWorld()->getStore().get<ESM::Faction>().find(lower);
+        if (it->second+1 < 10 && !faction->mRanks[it->second+1].empty())
+            it->second += 1;
+    }
+}
+
+void MWMechanics::NpcStats::lowerRank(const std::string &faction)
+{
+    const std::string lower = Misc::StringUtils::lowerCase(faction);
+    std::map<std::string, int>::iterator it = mFactionRank.find(lower);
+    if (it != mFactionRank.end())
+    {
+        it->second = std::max(0, it->second-1);
+    }
+}
+
+void MWMechanics::NpcStats::setFactionRank(const std::string &faction, int rank)
+{
+    const std::string lower = Misc::StringUtils::lowerCase(faction);
+    mFactionRank[lower] = rank;
+}
+
+void MWMechanics::NpcStats::joinFaction(const std::string& faction)
+{
+    const std::string lower = Misc::StringUtils::lowerCase(faction);
+    std::map<std::string, int>::iterator it = mFactionRank.find(lower);
+    if (it == mFactionRank.end())
+        mFactionRank[lower] = 0;
 }
 
 bool MWMechanics::NpcStats::getExpelled(const std::string& factionID) const
diff --git a/apps/openmw/mwmechanics/npcstats.hpp b/apps/openmw/mwmechanics/npcstats.hpp
index 4ea5d4578..ee897033b 100644
--- a/apps/openmw/mwmechanics/npcstats.hpp
+++ b/apps/openmw/mwmechanics/npcstats.hpp
@@ -70,7 +70,15 @@ namespace MWMechanics
             SkillValue& getSkill (int index);
 
             const std::map<std::string, int>& getFactionRanks() const;
-            std::map<std::string, int>& getFactionRanks();
+            /// Increase the rank in this faction by 1, if such a rank exists.
+            void raiseRank(const std::string& faction);
+            /// Lower the rank in this faction by 1, if such a rank exists.
+            void lowerRank(const std::string& faction);
+            /// Join this faction, setting the initial rank to 0.
+            void joinFaction(const std::string& faction);
+            /// Warning: this function performs no check whether the rank exists,
+            /// and should be used in initial actor setup only.
+            void setFactionRank(const std::string& faction, int rank);
 
             const std::set<std::string>& getExpelled() const { return mExpelled; }
             bool getExpelled(const std::string& factionID) const;
diff --git a/apps/openmw/mwscript/interpretercontext.cpp b/apps/openmw/mwscript/interpretercontext.cpp
index 21fee5f57..c43a010b4 100644
--- a/apps/openmw/mwscript/interpretercontext.cpp
+++ b/apps/openmw/mwscript/interpretercontext.cpp
@@ -310,7 +310,7 @@ namespace MWScript
 
     std::string InterpreterContext::getNPCRank() const
     {
-        std::map<std::string, int> ranks = getReferenceImp().getClass().getNpcStats (getReferenceImp()).getFactionRanks();
+        const std::map<std::string, int>& ranks = getReferenceImp().getClass().getNpcStats (getReferenceImp()).getFactionRanks();
         std::map<std::string, int>::const_iterator it = ranks.begin();
 
         MWBase::World *world = MWBase::Environment::get().getWorld();
@@ -348,7 +348,7 @@ namespace MWScript
 
         std::string factionId = getReferenceImp().getClass().getNpcStats (getReferenceImp()).getFactionRanks().begin()->first;
 
-        std::map<std::string, int> ranks = player.getClass().getNpcStats (player).getFactionRanks();
+        const std::map<std::string, int>& ranks = player.getClass().getNpcStats (player).getFactionRanks();
         std::map<std::string, int>::const_iterator it = ranks.find(factionId);
         int rank = -1;
         if (it != ranks.end())
@@ -375,7 +375,7 @@ namespace MWScript
 
         std::string factionId = getReferenceImp().getClass().getNpcStats (getReferenceImp()).getFactionRanks().begin()->first;
 
-        std::map<std::string, int> ranks = player.getClass().getNpcStats (player).getFactionRanks();
+        const std::map<std::string, int>& ranks = player.getClass().getNpcStats (player).getFactionRanks();
         std::map<std::string, int>::const_iterator it = ranks.find(factionId);
         int rank = -1;
         if (it != ranks.end())
diff --git a/apps/openmw/mwscript/statsextensions.cpp b/apps/openmw/mwscript/statsextensions.cpp
index c012cb12e..91f6d2abe 100644
--- a/apps/openmw/mwscript/statsextensions.cpp
+++ b/apps/openmw/mwscript/statsextensions.cpp
@@ -548,10 +548,7 @@ namespace MWScript
                     if(factionID != "")
                     {
                         MWWorld::Ptr player = MWBase::Environment::get().getWorld()->getPlayerPtr();
-                        if(player.getClass().getNpcStats(player).getFactionRanks().find(factionID) == player.getClass().getNpcStats(player).getFactionRanks().end())
-                        {
-                            player.getClass().getNpcStats(player).getFactionRanks()[factionID] = 0;
-                        }
+                        player.getClass().getNpcStats(player).joinFaction(factionID);
                     }
                 }
         };
@@ -585,13 +582,11 @@ namespace MWScript
                         MWWorld::Ptr player = MWBase::Environment::get().getWorld()->getPlayerPtr();
                         if(player.getClass().getNpcStats(player).getFactionRanks().find(factionID) == player.getClass().getNpcStats(player).getFactionRanks().end())
                         {
-                            player.getClass().getNpcStats(player).getFactionRanks()[factionID] = 0;
+                            player.getClass().getNpcStats(player).joinFaction(factionID);
                         }
                         else
                         {
-                            player.getClass().getNpcStats(player).getFactionRanks()[factionID] =
-                                    std::min(player.getClass().getNpcStats(player).getFactionRanks()[factionID] +1,
-                                             9);
+                            player.getClass().getNpcStats(player).raiseRank(factionID);
                         }
                     }
                 }
@@ -624,11 +619,7 @@ namespace MWScript
                     if(factionID != "")
                     {
                         MWWorld::Ptr player = MWBase::Environment::get().getWorld()->getPlayerPtr();
-                        if(player.getClass().getNpcStats(player).getFactionRanks().find(factionID) != player.getClass().getNpcStats(player).getFactionRanks().end())
-                        {
-                            player.getClass().getNpcStats(player).getFactionRanks()[factionID] =
-                                    std::max(0, player.getClass().getNpcStats(player).getFactionRanks()[factionID]-1);
-                        }
+                        player.getClass().getNpcStats(player).lowerRank(factionID);
                     }
                 }
         };
@@ -668,7 +659,7 @@ namespace MWScript
                     {
                         if(player.getClass().getNpcStats(player).getFactionRanks().find(factionID) != player.getClass().getNpcStats(player).getFactionRanks().end())
                         {
-                            runtime.push(player.getClass().getNpcStats(player).getFactionRanks()[factionID]);
+                            runtime.push(player.getClass().getNpcStats(player).getFactionRanks().at(factionID));
                         }
                         else
                         {
@@ -1036,8 +1027,7 @@ namespace MWScript
                     if (ptr == player)
                         return;
 
-                    std::map<std::string, int>& ranks = ptr.getClass().getNpcStats(ptr).getFactionRanks ();
-                    ranks[factionID] = std::min(9, ranks[factionID]+1);
+                    ptr.getClass().getNpcStats(ptr).raiseRank(factionID);
                 }
         };
 
@@ -1063,8 +1053,7 @@ namespace MWScript
                     if (ptr == player)
                         return;
 
-                    std::map<std::string, int>& ranks = ptr.getClass().getNpcStats(ptr).getFactionRanks ();
-                    ranks[factionID] = std::max(0, ranks[factionID]-1);
+                    ptr.getClass().getNpcStats(ptr).lowerRank(factionID);
                 }
         };