Add missing check for Replaces tag in replacement NEP

1 files changed, 6 insertions, 0 deletions

diff --git a/doc/neps/tools/build_index.py b/doc/neps/tools/build_index.py
index 134773065..65225c995 100644
--- a/doc/neps/tools/build_index.py
+++ b/doc/neps/tools/build_index.py
@@ -63,6 +63,12 @@ def nep_metadata():
             replaced_by = int(tags['Replaced-By'])
             replacement_nep = neps[replaced_by]
 
+            if not 'Replaces' in replacement_nep:
+                raise RuntimeError(
+                    f'NEP {nr} is superseded by {replaced_by}, but that NEP has '
+                    f"no Replaces tag."
+                )
+
             if not int(replacement_nep['Replaces']) == nr:
                 raise RuntimeError(
                     f'NEP {nr} is superseded by {replaced_by}, but that NEP has a '