diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0da3ba67d..41b57bf28 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@
     Bug #4746: Non-solid player can't run or sneak
     Bug #4750: Sneaking doesn't work in first person view if the player is in attack ready state
     Bug #4768: Fallback numerical value recovery chokes on invalid arguments
+    Bug #4778: Interiors of Illusion puzzle in Sotha Sil Expanded mod is broken
     Feature #2229: Improve pathfinding AI
     Feature #3442: Default values for fallbacks from ini file
     Feature #3610: Option to invert X axis
diff --git a/apps/openmw/mwscript/miscextensions.cpp b/apps/openmw/mwscript/miscextensions.cpp
index 0cf2fc464..d3b49239c 100644
--- a/apps/openmw/mwscript/miscextensions.cpp
+++ b/apps/openmw/mwscript/miscextensions.cpp
@@ -431,6 +431,12 @@ namespace MWScript
                     std::string effect = runtime.getStringLiteral(runtime[0].mInteger);
                     runtime.pop();
 
+                    if (!ptr.getClass().isActor())
+                    {
+                        runtime.push(0);
+                        return;
+                    }
+
                     char *end;
                     long key = strtol(effect.c_str(), &end, 10);
                     if(key < 0 || key > 32767 || *end != '\0')
@@ -659,6 +665,12 @@ namespace MWScript
                     std::string id = runtime.getStringLiteral(runtime[0].mInteger);
                     runtime.pop();
 
+                    if (!ptr.getClass().isActor())
+                    {
+                        runtime.push(0);
+                        return;
+                    }
+
                     const MWMechanics::CreatureStats& stats = ptr.getClass().getCreatureStats(ptr);
                     runtime.push(stats.getActiveSpells().isSpellActive(id) || stats.getSpells().isSpellActive(id));
                 }
diff --git a/apps/openmw/mwscript/statsextensions.cpp b/apps/openmw/mwscript/statsextensions.cpp
index 53316c44c..10d1252b9 100644
--- a/apps/openmw/mwscript/statsextensions.cpp
+++ b/apps/openmw/mwscript/statsextensions.cpp
@@ -536,7 +536,7 @@ namespace MWScript
 
                     Interpreter::Type_Integer value = 0;
 
-                    if (ptr.getClass().getCreatureStats(ptr).getSpells().hasSpell(id))
+                    if (ptr.getClass().isActor() && ptr.getClass().getCreatureStats(ptr).getSpells().hasSpell(id))
                         value = 1;
 
                     runtime.push (value);
diff --git a/components/esm/loadcrea.cpp b/components/esm/loadcrea.cpp
index 83315a5b8..f04439041 100644
--- a/components/esm/loadcrea.cpp
+++ b/components/esm/loadcrea.cpp
@@ -23,6 +23,7 @@ namespace ESM {
 
         mScale = 1.f;
         mHasAI = false;
+        mAiData.blank();
 
         bool hasName = false;
         bool hasNpdt = false;
@@ -160,7 +161,6 @@ namespace ESM {
         mSpells.mList.clear();
         mHasAI = false;
         mAiData.blank();
-        mAiData.mServices = 0;
         mAiPackage.mList.clear();
         mTransport.mList.clear();
     }
diff --git a/components/esm/loadnpc.cpp b/components/esm/loadnpc.cpp
index dd34934ad..6e7ba66c5 100644
--- a/components/esm/loadnpc.cpp
+++ b/components/esm/loadnpc.cpp
@@ -18,6 +18,7 @@ namespace ESM
         mInventory.mList.clear();
         mTransport.mList.clear();
         mAiPackage.mList.clear();
+        mAiData.blank();
         mHasAI = false;
 
         bool hasName = false;