diff --git a/src/cal_tools/files.py b/src/cal_tools/files.py
index 91766f0662f436cfa975eb566478c091c7d73071..cb0d527c0ae0eaecc201910f4b64d0e4754388ff 100644
--- a/src/cal_tools/files.py
+++ b/src/cal_tools/files.py
@@ -107,7 +107,7 @@ class DataFile(h5py.File):
 
     filename_format = '{prefix}-R{run:04d}-{aggregator}-S{sequence:05d}.h5'
     aggregator_pattern = re.compile(r'^[A-Z]{2,}\d{2}$')
-    instrument_source_pattern = re.compile(r'^[\w\/-]+:\w+$')
+    instrument_source_pattern = re.compile(r'^[\w\/-]+:[\w.]+$')
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)