diff --git a/src/control_backend/schemas/program.py b/src/control_backend/schemas/program.py
index 8f23cb9..1f3d1d9 100644
--- a/src/control_backend/schemas/program.py
+++ b/src/control_backend/schemas/program.py
@@ -7,7 +7,7 @@ University within the Software Project course.
 from enum import Enum
 from typing import Literal
 
-from pydantic import UUID4, BaseModel
+from pydantic import UUID4, BaseModel, field_validator
 
 
 class ProgramElement(BaseModel):
@@ -24,6 +24,13 @@ class ProgramElement(BaseModel):
     # To make program elements hashable
     model_config = {"frozen": True}
 
+    @field_validator("name")
+    @classmethod
+    def name_must_not_start_with_number(cls, v: str) -> str:
+        if v and v[0].isdigit():
+            raise ValueError('Field "name" must not start with a number.')
+        return v
+
 
 class LogicalOperator(Enum):
     """
@@ -105,6 +112,7 @@ class InferredBelief(ProgramElement):
     left: Belief
     right: Belief
 
+
 class EmotionBelief(ProgramElement):
     """
     Represents a belief that is set when a certain emotion is detected.
@@ -115,6 +123,7 @@ class EmotionBelief(ProgramElement):
     name: str = ""
     emotion: str
 
+
 class Norm(ProgramElement):
     """
     Base class for behavioral norms that guide the robot's interactions.
@@ -329,4 +338,4 @@ class Program(BaseModel):
 if __name__ == "__main__":
     input = input("Enter program JSON: ")
     program = Program.model_validate_json(input)
-    print(program)
\ No newline at end of file
+    print(program)