diff --git a/niche_vlaanderen/codetables.py b/niche_vlaanderen/codetables.py
index 04d81b3c..fe31be89 100644
--- a/niche_vlaanderen/codetables.py
+++ b/niche_vlaanderen/codetables.py
@@ -45,7 +45,11 @@ def check_lower_upper_boundaries(df, min_col, max_col, value):
     """
 
     group_cols = set(df.columns.tolist()) - {min_col, max_col, value}
-    for sel_group, subtable in df.groupby(list(group_cols)):
+    if len(list(group_cols)) > 0:
+        groups = list(group_cols)
+    else:
+        groups = list(group_cols)[0]
+    for sel_group, subtable in df.groupby(groups):
         min_values = subtable[min_col]
         max_values = subtable[max_col]
         for (i, index) in enumerate(min_values.index):
diff --git a/tests/test_validation.py b/tests/test_validation.py
index 66776a65..3cd35d0b 100644
--- a/tests/test_validation.py
+++ b/tests/test_validation.py
@@ -11,6 +11,7 @@
 
 def test_validation(zwarte_beek_niche, path_testdata):
     myniche = zwarte_beek_niche()
+    myniche.name = "zwarte beek"
     myniche.run()
 
     no = NicheValidation(