diff --git a/contracts/forms.py b/contracts/forms.py
index 886767d68f9b18ccead0db3f0bdaa74880ebfcaa..3a898eb046c5c996fbd1c3e97f2fc843f712ecf2 100644
--- a/contracts/forms.py
+++ b/contracts/forms.py
@@ -35,6 +35,7 @@ class SingnatureRepresentativeFormSet(BaseInlineFormSet):
                     attempted_signature_position.isnumeric()
                     and key.startswith("contractee_signatures-")
                     and key.endswith("-id")
+                    and value.isnumeric()
                 ):
                     signature_position = int(attempted_signature_position)
                     signature_id = int(value)