diff --git a/src/cobj.c b/src/cobj.c
index 0998b18..6263d8c 100644
--- a/src/cobj.c
+++ b/src/cobj.c
@@ -211,6 +211,7 @@ CObjString *cosmoO_takeString(CState *state, char *str, size_t sz) {
 
 CObjString *cosmoO_allocateString(CState *state, const char *str, size_t sz, uint32_t hash) {
     CObjString *strObj = (CObjString*)cosmoO_allocateBase(state, sizeof(CObjString), COBJ_STRING);
+    strObj->isIString = false;
     strObj->str = (char*)str;
     strObj->length = sz;
     strObj->hash = hash;
@@ -254,7 +255,10 @@ void cosmoO_setObject(CState *state, CObjObject *object, CValue key, CValue val)
         return;
     }
 
-    object->istringFlags = 0; // reset cache
+    // if the key is an IString, we need to reset the cache
+    if (IS_STRING(key) && ((CObjString*)cosmoV_readObj(key))->isIString)
+        object->istringFlags = 0; // reset cache
+
     if (IS_NIL(val)) { // if we're setting an index to nil, we can safely mark that as a tombstone
         cosmoT_remove(state, &object->tbl, key);
     } else {
diff --git a/src/cobj.h b/src/cobj.h
index a4bfce4..6ab7c7f 100644
--- a/src/cobj.h
+++ b/src/cobj.h
@@ -37,6 +37,7 @@ typedef struct CObj {
 
 typedef struct CObjString {
     CommonHeader; // "is a" CObj
+    bool isIString;
     int length;
     char *str;
     uint32_t hash; // for hashtable lookup
diff --git a/src/cstate.c b/src/cstate.c
index e68d793..c700a2a 100644
--- a/src/cstate.c
+++ b/src/cstate.c
@@ -49,6 +49,10 @@ CState *cosmoV_newState() {
     state->iStrings[ISTRING_GETTER] = cosmoO_copyString(state, "__getter", 8);
     state->iStrings[ISTRING_SETTER] = cosmoO_copyString(state, "__setter", 8);
 
+    // set the IString flags
+    for (int i = 0; i < ISTRING_MAX; i++)
+        state->iStrings[i]->isIString = true;
+
     return state;
 }
 
diff --git a/src/cstate.h b/src/cstate.h
index d38acde..9799f4e 100644
--- a/src/cstate.h
+++ b/src/cstate.h
@@ -14,7 +14,6 @@ typedef struct CCallFrame {
 
 typedef enum IStringEnum {
     ISTRING_INIT, // __init
-    ISTRING_EQUAL, // __equal
     ISTRING_INDEX, // __index
     ISTRING_NEWINDEX, // __newindex
     ISTRING_GETTER, // __getter