diff --git a/docs/changes/2692.bugfix.rst b/docs/changes/2692.bugfix.rst
new file mode 100644
index 00000000000..3546851841d
--- /dev/null
+++ b/docs/changes/2692.bugfix.rst
@@ -0,0 +1,2 @@
+Fix the function grouping telescope ids into ranges for
+the case of unsigned integer telescope ids.
diff --git a/src/ctapipe/instrument/subarray.py b/src/ctapipe/instrument/subarray.py
index f66bce99702..1cd94495e38 100644
--- a/src/ctapipe/instrument/subarray.py
+++ b/src/ctapipe/instrument/subarray.py
@@ -37,7 +37,7 @@ def _group_consecutives(sequence):
     from https://codereview.stackexchange.com/questions/214820/codewars-range-extraction
     """
     sequence = sorted(sequence)
-    for _, g in groupby(enumerate(sequence), lambda i_x: i_x[0] - i_x[1]):
+    for _, g in groupby(enumerate(sequence), lambda i_x: int(i_x[0]) - int(i_x[1])):
         r = [x for _, x in g]
         if len(r) > 2:
             yield f"{r[0]}-{r[-1]}"