diff --git a/examples/hello_world.l b/examples/hello_world.l
index 8bdb256..68b4c08 100644
--- a/examples/hello_world.l
+++ b/examples/hello_world.l
@@ -6,6 +6,5 @@ struct b {
 
 u32 test()
 {
-	u32 a = (u32)3;
-	a = (u32)2;
+	f32 a = 5.0;
 }
diff --git a/sema.c b/sema.c
index a1499a4..15ea070 100644
--- a/sema.c
+++ b/sema.c
@@ -22,6 +22,9 @@ static scope *global_scope = NULL;
 static scope *current_scope = NULL;
 static type *current_return = NULL;
 
+static type *const_int = NULL;
+static type *const_float = NULL;
+
 static bool in_loop = false;
 
 /* Print the error message and sync the parser. */
@@ -422,6 +425,21 @@ static type *get_identifier_type(sema *s, ast_node *node)
 
 static bool match(type *t1, type *t2);
 
+static bool can_cast(type *source, type *dest)
+{
+	if (!dest || !source) return false;
+
+	switch (dest->tag) {
+		case TYPE_INTEGER:
+		case TYPE_UINTEGER:
+			return source->tag == TYPE_INTEGER_CONST;
+		case TYPE_FLOAT:
+			return source->tag == TYPE_FLOAT_CONST;
+		default:
+			return false;
+	}
+}
+
 static type *get_expression_type(sema *s, ast_node *node)
 {
 	if (!node) {
@@ -434,9 +452,9 @@ static type *get_expression_type(sema *s, ast_node *node)
 		case NODE_IDENTIFIER:
 			return get_identifier_type(s, node);
 		case NODE_INTEGER:
-			return shget(type_reg, "i32");
+			return const_int;
 		case NODE_FLOAT:
-			return shget(type_reg, "f64");
+			return const_float;
 		case NODE_STRING:
 			return get_string_type(s, node);
 		case NODE_CHAR:
@@ -514,6 +532,9 @@ static bool match(type *t1, type *t2)
 		case TYPE_GENERIC:
 			/* TODO */
 			return false;
+		case TYPE_INTEGER_CONST:
+		case TYPE_FLOAT_CONST:
+			return false;
 	}
 
 	return false;
@@ -600,7 +621,7 @@ static void check_statement(sema *s, ast_node *node)
 				error(node, "redeclaration of variable.");
 				break;
 			}
-			if (!match(t, get_expression_type(s, node->expr.var_decl.value))) {
+			if (!can_cast(get_expression_type(s, node->expr.var_decl.value), t) && !match(t, get_expression_type(s, node->expr.var_decl.value))) {
 				error(node, "type mismatch.");
 			}
 			shput(current_scope->defs, name, t);
@@ -685,6 +706,16 @@ sema *sema_init(parser *p, arena *a)
 	register_type(s, "f32", create_float(s, "f32", 32));
 	register_type(s, "f64", create_float(s, "f64", 64));
 
+	const_int = arena_alloc(s->allocator, sizeof(type));
+	const_int->name = "const_int";
+	const_int->tag = TYPE_INTEGER_CONST;
+	const_int->data.integer = 0;
+
+	const_float = arena_alloc(s->allocator, sizeof(type));
+	const_float->name = "const_float";
+	const_float->tag = TYPE_FLOAT_CONST;
+	const_float->data.flt = 0;
+
 	analyze_unit(s, s->ast);
 
 	return s;
diff --git a/sema.h b/sema.h
index 47832b7..a1f4285 100644
--- a/sema.h
+++ b/sema.h
@@ -12,7 +12,9 @@ typedef enum {
 	TYPE_PTR,
 	TYPE_SLICE,
 	TYPE_FLOAT,
+	TYPE_FLOAT_CONST,
 	TYPE_INTEGER,
+	TYPE_INTEGER_CONST,
 	TYPE_UINTEGER,
 	TYPE_STRUCT,
 	TYPE_UNION,