diff --git a/.gitignore b/.gitignore
index 3b554e7..0c13b8e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,4 +9,6 @@ test
 
 vgcore.*
 *.gcov
-lib*.a
\ No newline at end of file
+lib*.a
+
+*.noja
\ No newline at end of file
diff --git a/src/lib/builtins/basic.c b/src/lib/builtins/basic.c
index a6ae85a..a9259fe 100644
--- a/src/lib/builtins/basic.c
+++ b/src/lib/builtins/basic.c
@@ -299,6 +299,25 @@ static int bin_error(Runtime *runtime, Object **argv, unsigned int argc, Object
 	return -1;
 }
 
+static int bin_istypeof(Runtime *runtime, Object **argv, unsigned int argc, Object *rets[static MAX_RETS], Error *error)
+{
+	UNUSED(argc);
+	UNUSED(rets);
+	UNUSED(runtime);
+
+	ASSERT(argc == 2);
+
+	bool yes = Object_IsTypeOf(argv[0], argv[1]);
+
+	Heap *heap = Runtime_GetHeap(runtime);
+	Object *o_yes = Object_FromBool(yes, heap, error);
+	if (o_yes == NULL)
+		return -1;
+
+	rets[0] = o_yes;
+	return 1;
+}
+
 void bins_basic_init(StaticMapSlot slots[])
 {
 	slots[0].as_type = Object_GetTypeType();
@@ -311,6 +330,7 @@ void bins_basic_init(StaticMapSlot slots[])
 	slots[7].as_type = Object_GetMapType();
 	slots[8].as_type = Object_GetFileType();
 	slots[9].as_type = Object_GetDirType();
+	slots[10].as_type = Object_GetNullableType();
 }
 
 StaticMapSlot bins_basic[] = {
@@ -324,6 +344,7 @@ StaticMapSlot bins_basic[] = {
 	{ TYPENAME_MAP,    SM_TYPE, .as_type = NULL /* Until bins_basic_init is called */ },
 	{ TYPENAME_FILE,   SM_TYPE, .as_type = NULL /* Until bins_basic_init is called */ },
 	{ TYPENAME_DIRECTORY, SM_TYPE, .as_type = NULL /* Until bins_basic_init is called */ },
+	{ TYPENAME_NULLABLE,  SM_TYPE, .as_type = NULL },
 	
 	{ "math",   SM_SMAP, .as_smap = bins_math,   },
 	{ "files",  SM_SMAP, .as_smap = bins_files,  },
@@ -331,11 +352,12 @@ StaticMapSlot bins_basic[] = {
 	{ "string", SM_SMAP, .as_smap = bins_string, },
 	
 	{ "import", SM_FUNCT, .as_funct = bin_import, .argc = 1, },
-	{ "type", SM_FUNCT, .as_funct = bin_type, .argc = 1 },
-	{ "print", SM_FUNCT, .as_funct = bin_print, .argc = -1 },
-	{ "input", SM_FUNCT, .as_funct = bin_input, .argc = 0 },
-	{ "count", SM_FUNCT, .as_funct = bin_count, .argc = 1 },
-	{ "error", SM_FUNCT, .as_funct = bin_error, .argc = 1 },
+	{ "type",   SM_FUNCT, .as_funct = bin_type, .argc = 1 },
+	{ "print",  SM_FUNCT, .as_funct = bin_print, .argc = -1 },
+	{ "input",  SM_FUNCT, .as_funct = bin_input, .argc = 0 },
+	{ "count",  SM_FUNCT, .as_funct = bin_count, .argc = 1 },
+	{ "error",  SM_FUNCT, .as_funct = bin_error, .argc = 1 },
 	{ "assert", SM_FUNCT, .as_funct = bin_assert, .argc = -1 },
+	{ "istypeof", SM_FUNCT, .as_funct = bin_istypeof, .argc = 2, },
 	{ NULL, SM_END, {}, {} },
 };
diff --git a/src/lib/common/defs.h b/src/lib/common/defs.h
index 5a5fa99..1af4e87 100644
--- a/src/lib/common/defs.h
+++ b/src/lib/common/defs.h
@@ -12,4 +12,6 @@
 #define TYPENAME_BUFFER "Buffer"
 
 #define TYPENAME_FILE      "File"
-#define TYPENAME_DIRECTORY "Directory"
\ No newline at end of file
+#define TYPENAME_DIRECTORY "Directory"
+
+#define TYPENAME_NULLABLE "NullableType"
\ No newline at end of file
diff --git a/src/lib/common/executable.c b/src/lib/common/executable.c
index bed2561..397945b 100644
--- a/src/lib/common/executable.c
+++ b/src/lib/common/executable.c
@@ -82,6 +82,7 @@ static const InstrInfo instr_table[] = {
 	[OPCODE_GRT]     = {"GRT",  0, NULL},
 	[OPCODE_LEQ]     = {"LEQ",  0, NULL},
 	[OPCODE_GEQ]     = {"GEQ",  0, NULL},
+	[OPCODE_NLB]     = {"NLB",  0, NULL},
 	[OPCODE_ASS]     = {"ASS",  1, (OperandType[]) {OPTP_STRING}},
 	[OPCODE_POP]     = {"POP",  1, (OperandType[]) {OPTP_INT}},
 	[OPCODE_CALL]    = {"CALL", 2, (OperandType[]) {OPTP_INT, OPTP_INT}},
diff --git a/src/lib/common/executable.h b/src/lib/common/executable.h
index 600dd26..3b79738 100644
--- a/src/lib/common/executable.h
+++ b/src/lib/common/executable.h
@@ -67,6 +67,7 @@ typedef enum {
 	OPCODE_GRT,
 	OPCODE_LEQ,
 	OPCODE_GEQ,
+	OPCODE_NLB,
 	OPCODE_ASS,
 	OPCODE_POP,
 	OPCODE_CALL,
diff --git a/src/lib/compiler/ASTi.h b/src/lib/compiler/ASTi.h
index 42bfb38..aedcd6d 100644
--- a/src/lib/compiler/ASTi.h
+++ b/src/lib/compiler/ASTi.h
@@ -77,6 +77,9 @@ typedef enum {
 	EXPR_STRING,
 	EXPR_IDENT,
 	EXPR_SELECT,
+
+	EXPR_NULLABLETYPE,
+	EXPR_SUMTYPE,
 } ExprKind;
 
 typedef struct Node Node;
diff --git a/src/lib/compiler/codegen.c b/src/lib/compiler/codegen.c
index 57fdc7f..e4885c6 100644
--- a/src/lib/compiler/codegen.c
+++ b/src/lib/compiler/codegen.c
@@ -174,6 +174,7 @@ static Opcode exprkind_to_opcode(ExprKind kind)
 {
 	switch(kind)
 	{
+		case EXPR_NULLABLETYPE: return OPCODE_NLB;
 		case EXPR_NOT: return OPCODE_NOT;
 		case EXPR_POS: return OPCODE_POS;
 		case EXPR_NEG: return OPCODE_NEG;
@@ -475,10 +476,13 @@ static void emitInstrForExprNode(CodegenContext *ctx, ExprNode *expr,
 	switch(expr->kind)
 	{
 		case EXPR_PAIR:
-		CodegenContext_ReportErrorAndJump(ctx, 0, "Tuple outside of assignment or return statement");
+		CodegenContext_ReportErrorAndJump(
+			ctx, 0, "Tuple outside of "
+			"assignment or return statement");
 		UNREACHABLE;
 		return; // For the compiler warning.
 
+		case EXPR_NULLABLETYPE:
 		case EXPR_NOT:
 		case EXPR_POS: case EXPR_NEG:
 		case EXPR_ADD: case EXPR_SUB:
diff --git a/src/lib/compiler/parse.c b/src/lib/compiler/parse.c
index 45bd649..0456b33 100644
--- a/src/lib/compiler/parse.c
+++ b/src/lib/compiler/parse.c
@@ -63,6 +63,7 @@
 
 typedef enum {
 	
+	TOPT = '?',
 	TPOS = '+',
 	TNEG = '-',
 	
@@ -556,6 +557,7 @@ static Node *parse_statement(Context *ctx)
 		case '[':
 		case '+':
 		case '-':
+		case '?':
 		case TINT:
 		case TFLOAT:
 		case TSTRING:
@@ -1544,6 +1546,7 @@ static Node *parse_prefix_expression(Context *ctx)
 
 		case '+':
 		case '-':
+		case '?':
 		case TKWNOT:
 		{
 			Token *unary_operator = current_token(ctx);
@@ -1569,6 +1572,7 @@ static Node *parse_prefix_expression(Context *ctx)
 
 				switch(unary_operator->kind)
 				{
+					case '?': temp->base.kind = EXPR_NULLABLETYPE; break;
 					case '+': temp->base.kind = EXPR_POS; break;
 					case '-': temp->base.kind = EXPR_NEG; break;
 					case TKWNOT: temp->base.kind = EXPR_NOT; break;
@@ -2217,4 +2221,4 @@ static Node *parse_dowhile_statement(Context *ctx)
 	}
 
 	return (Node*) dowhl;
-}
+}
\ No newline at end of file
diff --git a/src/lib/objects/o_nullable.c b/src/lib/objects/o_nullable.c
new file mode 100644
index 0000000..b7715a8
--- /dev/null
+++ b/src/lib/objects/o_nullable.c
@@ -0,0 +1,62 @@
+#include "../common/defs.h" 
+#include "objects.h"
+
+static void walk(Object *self, void (*callback)(Object **referer, void *userp), void *userp);
+static bool istypeof(Object *self, Object *other);
+
+typedef struct {
+    Object  base;
+    Object *item;
+} NullableObject;
+
+static TypeObject t_nullable = {
+    .base = (Object) { .type = &t_type, .flags = Object_STATIC },
+    .name = TYPENAME_NULLABLE,
+    .size = sizeof(NullableObject),
+    .init = NULL,
+    .free = NULL,
+    .hash = NULL,
+    .copy = NULL,
+    .call = NULL,
+    .print = NULL,
+
+    .select = NULL,
+    .delete = NULL,
+    .insert = NULL,
+    .count  = NULL,
+
+    .istypeof = istypeof,
+
+    .op_eql = NULL,
+    .walk = walk,
+    .walkexts = NULL,
+};
+
+TypeObject *Object_GetNullableType()
+{
+    return &t_nullable;
+}
+
+Object *Object_NewNullable(Object *item, Heap *heap, Error *error)
+{
+    NullableObject *nullable = (NullableObject*) Heap_Malloc(heap, &t_nullable, error);
+    if (nullable != NULL)
+        nullable->item = item;
+    return (Object*) nullable;
+}
+
+static bool 
+istypeof(Object *self, 
+         Object *other)
+{
+    NullableObject *nullable = (NullableObject*) self;
+    if (Object_IsNone(other))
+        return true;
+    return Object_IsTypeOf(nullable->item, other);
+}
+
+static void walk(Object *self, void (*callback)(Object **referer, void *userp), void *userp)
+{
+    NullableObject *nullable = (NullableObject*) self;
+    callback(&nullable->item, userp);
+}
\ No newline at end of file
diff --git a/src/lib/objects/objects.c b/src/lib/objects/objects.c
index 4ec6869..189593d 100644
--- a/src/lib/objects/objects.c
+++ b/src/lib/objects/objects.c
@@ -33,14 +33,21 @@
 #include "../common/defs.h"
 
 static _Bool op_eql(Object *self, Object *other);
+static bool istypeof(Object *self, Object *other);
 
 TypeObject t_type = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = TYPENAME_TYPE,
 	.size = sizeof(TypeObject),
+	.istypeof = istypeof,
 	.op_eql = op_eql,
 };
 
+static bool istypeof(Object *self, Object *other)
+{
+    return other->type == (TypeObject*) self;
+}
+
 TypeObject *Object_GetTypeType()
 {
 	return &t_type;
@@ -71,6 +78,13 @@ const TypeObject *Object_GetType(const Object *obj)
 	return obj->type;
 }
 
+bool Object_IsTypeOf(Object *typ, Object *obj)
+{
+	if (typ->type->istypeof == NULL)
+		return false;
+	return typ->type->istypeof(typ, obj);
+}
+
 int Object_Hash(Object *obj)
 {
 	ASSERT(obj != NULL);
diff --git a/src/lib/objects/objects.h b/src/lib/objects/objects.h
index 94b5a02..b3f8d42 100644
--- a/src/lib/objects/objects.h
+++ b/src/lib/objects/objects.h
@@ -72,6 +72,9 @@ struct TypeObject {
 	bool    (*insert)(Object *self, Object *key, Object *val, Heap *heap, Error *err);
 	int 	(*count)(Object *self);
 
+	// Types.
+	bool (*istypeof)(Object *self, Object *other);
+
 	bool (*op_eql)(Object *self, Object *other);
 	void (*walk)    (Object *self, void (*callback)(Object **referer,                    void *userp), void *userp);
 	void (*walkexts)(Object *self, void (*callback)(void   **referer, unsigned int size, void *userp), void *userp);
@@ -100,6 +103,7 @@ int 		 Object_Hash (Object *obj);
 Object*		 Object_Copy (Object *obj, Heap *heap, Error *err);
 int          Object_Call (Object *obj, Object **argv, unsigned int argc, Object *rets[static MAX_RETS], Heap *heap, Error *err);
 void 		 Object_Print(Object *obj, FILE *fp);
+bool 		 Object_IsTypeOf(Object *typ, Object *obj);
 Object*		 Object_Select(Object *coll, Object *key, Heap *heap, Error *err);
 Object*		 Object_Delete(Object *coll, Object *key, Heap *heap, Error *err);
 bool 		 Object_Insert(Object *coll, Object *key, Object *val, Heap *heap, Error *err);
@@ -114,6 +118,7 @@ Object*		 Object_NewNone(Heap *heap, Error *error);
 Object*      Object_NewBuffer(size_t size, Heap *heap, Error *error);
 Object*		 Object_NewClosure(Object *parent, Object *new_map, Heap *heap, Error *error);
 Object*      Object_SliceBuffer(Object *obj, size_t offset, size_t length, Heap *heap, Error *error);
+Object*      Object_NewNullable(Object *item, Heap *heap, Error *error);
 
 Object*		 Object_FromInt   (long long int val, Heap *heap, Error *error);
 Object*		 Object_FromBool  (bool 		 val, Heap *heap, Error *error);
@@ -133,6 +138,7 @@ TypeObject *Object_GetMapType();
 TypeObject *Object_GetBufferType();
 TypeObject *Object_GetFileType();
 TypeObject *Object_GetDirType();
+TypeObject *Object_GetNullableType();
 
 bool  Object_IsNone(Object *obj);
 bool  Object_IsInt(Object *obj);
diff --git a/src/lib/runtime/runtime.c b/src/lib/runtime/runtime.c
index 3340851..60f208b 100644
--- a/src/lib/runtime/runtime.c
+++ b/src/lib/runtime/runtime.c
@@ -653,6 +653,32 @@ static _Bool step(Runtime *runtime, Error *error)
 			return 1;
 		}
 
+		case OPCODE_NLB:
+		{
+			ASSERT(opc == 0);
+
+			if(runtime->frame->used == 0)
+			{
+				Error_Report(error, 1, "Frame doesn't have enough items on the stack to execute NLB");
+				return 0;
+			}
+
+			Object *top = Stack_Top(runtime->stack, 0);
+
+			if(!Runtime_Pop(runtime, error, 1))
+				return 0;
+			
+			ASSERT(top != NULL);
+
+			Object *nullable = Object_NewNullable(top, runtime->heap, error);
+			if(nullable == NULL)
+				return 0;
+
+			if(!Runtime_Push(runtime, error, nullable))
+				return 0;
+			return 1;
+		}
+
 		case OPCODE_ADD:
 		case OPCODE_SUB:
 		case OPCODE_MUL: