diff --git a/src/_pytest/python.py b/src/_pytest/python.py
index cbb82e390..0e9bd2126 100644
--- a/src/_pytest/python.py
+++ b/src/_pytest/python.py
@@ -1002,7 +1002,14 @@ class IdMaker:
             # Suffix non-unique IDs to make them unique.
             for index, id in enumerate(resolved_ids):
                 if id_counts[id] > 1:
-                    resolved_ids[index] = f"{id}{id_suffixes[id]}"
+                    suffix = ""
+                    if id[-1].isdigit():
+                        suffix = "_"
+                    new_id = f"{id}{suffix}{id_suffixes[id]}"
+                    while new_id in set(resolved_ids):
+                        id_suffixes[id] += 1
+                        new_id = f"{id}{suffix}{id_suffixes[id]}"
+                    resolved_ids[index] = new_id
                     id_suffixes[id] += 1
         return resolved_ids