diff --git a/src/card.py b/src/card.py
index 1bd0473..b427eb8 100644
--- a/src/card.py
+++ b/src/card.py
@@ -96,7 +96,9 @@ def remove_created_at(cls, values: dict) -> dict:
 
 
 class CardQuery(BaseModel):
-    number: str = Field(..., description="Card number to be queried")
+    number: constr(min_length=1, max_length=128, pattern="^[a-zA-Z0-9]+$") = Field(
+        ..., description="Card number to be queried"
+    )
 
 
 class CardResponse(CardModel):