diff --git a/ifpd2/probe.py b/ifpd2/probe.py
index d02defbb..3e34587b 100644
--- a/ifpd2/probe.py
+++ b/ifpd2/probe.py
@@ -549,7 +549,8 @@ def reduce_probe_list(self, probe_list):
             print(e)
             raise
 
-    def select_probe_from_pair(self, probeA, probeB):
+    @staticmethod
+    def select_probe_from_pair(probeA, probeB):
         if probeA.size < probeB.size:
             return probeA
         else:
diff --git a/ifpd2/probe_set.py b/ifpd2/probe_set.py
index be27f4f0..8c51e250 100644
--- a/ifpd2/probe_set.py
+++ b/ifpd2/probe_set.py
@@ -183,7 +183,8 @@ def __init__(self, out_path):
             shutil.rmtree(out_path)
         os.mkdir(out_path)
 
-    def __build_probe_set_list(self, window_list, i):
+    @staticmethod
+    def __build_probe_set_list(window_list, i):
         probe_set_list = [(p,) for p in window_list[i]]
 
         for w in window_list[(i + 1) :]: