diff --git a/engine/memobj.c b/engine/memobj.c
index a09407a..18138cd 100644
--- a/engine/memobj.c
+++ b/engine/memobj.c
@@ -401,7 +401,7 @@ PH7_PRIVATE sxi32 PH7_CheckVarCompat(ph7_value *pObj, int nType) {
  * destination are of the compatible data types.
  */
 PH7_PRIVATE sxi32 PH7_MemObjSafeStore(ph7_value *pSrc, ph7_value *pDest) {
-	if(pDest->nType == 0 || ((pDest->nType | MEMOBJ_FIXEDVAL | MEMOBJ_PARENTOBJ) == (pSrc->nType | MEMOBJ_FIXEDVAL | MEMOBJ_PARENTOBJ))) {
+	if(pDest->nType == 0 || pDest->nType == pSrc->nType) {
 		PH7_MemObjStore(pSrc, pDest);
 	} else if(pDest->nType & MEMOBJ_MIXED) {
 		if(pDest->nType & MEMOBJ_HASHMAP) {
diff --git a/engine/vm.c b/engine/vm.c
index ad225ed..5819f5d 100644
--- a/engine/vm.c
+++ b/engine/vm.c
@@ -2765,7 +2765,7 @@ static sxi32 VmByteCodeExec(
 					if(pObj == 0) {
 						PH7_VmThrowError(&(*pVm), PH7_CTX_ERR,
 										"Variable '$%z' undeclared (first use in this method/closure)", &sName);
-					} else if(pObj->iFlags & MEMOBJ_FIXEDVAL) {
+					} else if(pObj->iFlags != MEMOBJ_VARIABLE) {
 						PH7_VmThrowError(&(*pVm), PH7_CTX_ERR, "Cannot re-assign a value of '$%z' statement", &sName);
 					}
 					if(!pInstr->p3) {
@@ -4154,7 +4154,7 @@ static sxi32 VmByteCodeExec(
 							pThis = (ph7_class_instance *)pNos->x.pOther;
 							/* Point to the instantiated class */
 							pClass = pThis->pClass;
-							if(pNos->iFlags & MEMOBJ_PARENTOBJ) {
+							if(pNos->iFlags == MEMOBJ_PARENTOBJ) {
 								if(pClass->pBase == 0) {
 									PH7_VmThrowError(&(*pVm), PH7_CTX_ERR,
 													"Attempt to call parent class from non-inheritance instance of class '%z'", &pClass->sName);
@@ -4175,7 +4175,7 @@ static sxi32 VmByteCodeExec(
 												  &pClass->sName, &sName
 												 );
 								} else {
-									if(pNos->iFlags & MEMOBJ_PARENTOBJ && pMeth->iProtection == PH7_CLASS_PROT_PRIVATE) {
+									if(pNos->iFlags == MEMOBJ_PARENTOBJ && pMeth->iProtection == PH7_CLASS_PROT_PRIVATE) {
 										PH7_VmThrowError(&(*pVm), PH7_CTX_ERR,
 												"Access to the class method '%z->%z()' is forbidden", &pClass->sName, &sName);
 									}
@@ -4572,7 +4572,7 @@ static sxi32 VmByteCodeExec(
 									pThis = (ph7_class_instance *)pTarget->x.pOther;
 									pThis->iRef += 2;
 									pClass = pThis->pClass;
-									if(pTarget->iFlags & MEMOBJ_PARENTOBJ) {
+									if(pTarget->iFlags == MEMOBJ_PARENTOBJ) {
 										/* Parent called */
 										if(pThis->pClass->pBase == 0) {
 											PH7_VmThrowError(&(*pVm), PH7_CTX_ERR,
@@ -4648,18 +4648,18 @@ static sxi32 VmByteCodeExec(
 							pObj = VmCreateMemObj(&(*pVm), &sParent, TRUE);
 							if(pObj) {
 								/* Reflect the change */
+								pObj->iFlags = MEMOBJ_PARENTOBJ;
 								pObj->x.pOther = pThis;
 								MemObjSetType(pObj, MEMOBJ_OBJ);
-								pObj->iFlags |= MEMOBJ_FIXEDVAL | MEMOBJ_PARENTOBJ;
 							}
 							/* Install the '$this' variable */
 							static const SyString sThis = { "this", sizeof("this") - 1 };
 							pObj = VmCreateMemObj(&(*pVm), &sThis, TRUE);
 							if(pObj) {
 								/* Reflect the change */
+								pObj->iFlags = MEMOBJ_THISOBJ;
 								pObj->x.pOther = pThis;
 								MemObjSetType(pObj, MEMOBJ_OBJ);
-								pObj->iFlags |= MEMOBJ_FIXEDVAL;
 							}
 						}
 						if(SySetUsed(&pVmFunc->aStatic) > 0) {
diff --git a/include/ph7int.h b/include/ph7int.h
index 7d2cc45..2c3b6cc 100644
--- a/include/ph7int.h
+++ b/include/ph7int.h
@@ -631,8 +631,10 @@ struct ph7_value {
 	sxu32 nIdx;         /* Index number of this entry in the global object allocator */
 };
 /* Variable control flags */
-#define MEMOBJ_FIXEDVAL  0x1000  /* Memory value is fixed and cannot be modified */
-#define MEMOBJ_PARENTOBJ 0x2000  /* Memory value is a parent object */
+#define MEMOBJ_VARIABLE  0 /* Memory value is variable */
+#define MEMOBJ_BASEOBJ   1 /* Memory value is 'base' object */
+#define MEMOBJ_PARENTOBJ 2 /* Memory value is 'parent' object */
+#define MEMOBJ_THISOBJ   3 /* Memory value is 'this' object */
 /* Allowed variable data types.
  */
 #define MEMOBJ_BOOL      0x0001  /* Memory value is a boolean */