diff --git a/workflow/scripts/collect-fp-fn.py b/workflow/scripts/collect-fp-fn.py
index a84161e..82473a1 100644
--- a/workflow/scripts/collect-fp-fn.py
+++ b/workflow/scripts/collect-fp-fn.py
@@ -82,7 +82,7 @@ def get_idx_sorted_by_clustering(data):
 
     data = data.dropna(how="all")
 
-    if not data.empty and data.shape[1] > 1:
+    if data.shape[1] > 1 and data.shape[0] > 1:
         idx_rows = get_idx_sorted_by_clustering(data)
         idx_cols = get_idx_sorted_by_clustering(data.T)
         data = data.iloc[idx_rows, idx_cols]