diff --git a/datatypes.py b/datatypes.py
index a2f17fd..a44d443 100644
--- a/datatypes.py
+++ b/datatypes.py
@@ -13,11 +13,29 @@ class Datatype(Enum):
     COMPLEX = auto()
 
 
+@dataclass
+class Data:
+    type: Datatype
+    value: Any
+
+
 @dataclass
 class Variable:
     name: str
     type: Datatype
-    value: Any
+    value: Data
+
+    def __setattr__(self, name, value):
+        if name == "value" and isinstance(value, Data):
+            if self.type == value.type:
+                object.__setattr__(self, name, value)
+            else:
+                raise ValueError(
+                    "Type inequality; cannot assign value of "
+                    f"type {value.type} to variable of type {self.type}"
+                )
+        else:
+            object.__setattr__(self, name, value)
 
 
 NONE_TYPE = Variable(None, Datatype.NONE, None)