diff --git a/src/chunk.h b/src/chunk.h
index 1391848..57dd822 100644
--- a/src/chunk.h
+++ b/src/chunk.h
@@ -65,7 +65,8 @@ typedef enum {
 	OP_FILTER_EXCEPT,
 	OP_CREATE_CLASSMETHOD,
 	OP_INVOKE_ITER,
-	/* current highest: 41 */
+	OP_INVOKE_CONTAINS,
+	/* current highest: 42 */
 
 	OP_CALL = 64,
 	OP_CLASS,
diff --git a/src/compiler.c b/src/compiler.c
index 519a9c5..37d9d78 100644
--- a/src/compiler.c
+++ b/src/compiler.c
@@ -624,11 +624,7 @@ _dotDone:
 
 static void in_(int canAssign) {
 	parsePrecedence(PREC_COMPARISON);
-	KrkToken contains = syntheticToken("__contains__");
-	ssize_t ind = identifierConstant(&contains);
-	EMIT_CONSTANT_OP(OP_GET_PROPERTY, ind);
-	emitByte(OP_SWAP);
-	emitBytes(OP_CALL,1);
+	emitByte(OP_INVOKE_CONTAINS);
 }
 
 static void not_(int canAssign) {
diff --git a/src/object.h b/src/object.h
index e7b7aa8..9b651ee 100644
--- a/src/object.h
+++ b/src/object.h
@@ -180,6 +180,7 @@ typedef struct KrkClass {
 	KrkObj * _dir;
 	KrkObj * _setslice;
 	KrkObj * _delslice;
+	KrkObj * _contains;
 } KrkClass;
 
 /**
diff --git a/src/opcodes.h b/src/opcodes.h
index 68c3667..095a946 100644
--- a/src/opcodes.h
+++ b/src/opcodes.h
@@ -31,6 +31,7 @@ SIMPLE(OP_INVOKE_GETSLICE)
 SIMPLE(OP_INVOKE_SETSLICE)
 SIMPLE(OP_INVOKE_DELSLICE)
 SIMPLE(OP_INVOKE_ITER)
+SIMPLE(OP_INVOKE_CONTAINS)
 SIMPLE(OP_SWAP)
 SIMPLE(OP_FINALIZE)
 SIMPLE(OP_IS)
diff --git a/src/vm.c b/src/vm.c
index 5e0a00a..26835b2 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -458,6 +458,7 @@ void krk_finalizeClass(KrkClass * _class) {
 		{&_class->_iter, METHOD_ITER},
 		{&_class->_getattr, METHOD_GETATTR},
 		{&_class->_dir, METHOD_DIR},
+		{&_class->_contains, METHOD_CONTAINS},
 		{NULL, 0},
 	};
 
@@ -1185,6 +1186,7 @@ void krk_initVM(int flags) {
 		_(METHOD_ITER, "__iter__"),
 		_(METHOD_GETATTR, "__getattr__"),
 		_(METHOD_DIR, "__dir__"),
+		_(METHOD_CONTAINS, "__contains__"),
 	#undef _
 	};
 	for (size_t i = 0; i < METHOD__MAX; ++i) {
@@ -2009,6 +2011,16 @@ static KrkValue run() {
 				}
 				break;
 			}
+			case OP_INVOKE_CONTAINS: {
+				KrkClass * type = krk_getType(krk_peek(0));
+				if (likely(type->_contains)) {
+					krk_swap(1);
+					krk_push(krk_callSimple(OBJECT_VAL(type->_contains), 2, 0));
+				} else {
+					krk_runtimeError(vm.exceptions->attributeError, "'%s' object can not be tested for membership", krk_typeName(krk_peek(0)));
+				}
+				break;
+			}
 			case OP_FINALIZE: {
 				KrkClass * _class = AS_CLASS(krk_peek(0));
 				/* Store special methods for quick access */
diff --git a/src/vm.h b/src/vm.h
index a00344d..d009540 100644
--- a/src/vm.h
+++ b/src/vm.h
@@ -90,6 +90,7 @@ typedef enum {
 	METHOD_DIR,
 	METHOD_SETSLICE,
 	METHOD_DELSLICE,
+	METHOD_CONTAINS,
 
 	METHOD__MAX,
 } KrkSpecialMethods;