diff --git a/invisible_cities/cities/components.py b/invisible_cities/cities/components.py
index 0626d242d..842c24ecd 100644
--- a/invisible_cities/cities/components.py
+++ b/invisible_cities/cities/components.py
@@ -117,7 +117,12 @@ def proxy(**kwds):
             conf.files_in = [conf.files_in]
 
         globbed_files = map(glob, map(expandvars, conf.files_in))
-        conf.files_in = sorted(f for fs in globbed_files for f in fs)
+        globbed_files = sorted(f for fs in globbed_files for f in fs)
+        if len(set(globbed_files)) != len(globbed_files):
+            warnings.warn("files_in contains repeated values. Ignoring duplicate files.", UserWarning)
+            globbed_files = sorted(set(globbed_files))
+
+        conf.files_in = globbed_files
         conf.file_out = expandvars(conf.file_out)
 
         conf.event_range  = event_range(conf)
diff --git a/invisible_cities/cities/components_test.py b/invisible_cities/cities/components_test.py
index 3d2e62ece..e81c94a83 100644
--- a/invisible_cities/cities/components_test.py
+++ b/invisible_cities/cities/components_test.py
@@ -110,6 +110,7 @@ def write_config_file(filename, **kwargs):
                      , ["electrons_511keV_z250_RWF.h5" , "electrons_1250keV_z250_RWF.h5", "electrons_2500keV_z250_RWF.h5"] )
                    )
                  )
+@mark.filterwarnings("ignore:files_in contains repeated values")
 def test_city_files_in(case_, files_in, expected, config_tmpdir, ICDATADIR):
     """
     Check that all possible files_in inputs are handled properly: