diff --git a/src/neat/trees/phystree.py b/src/neat/trees/phystree.py
index 37b23ca5..135ec870 100755
--- a/src/neat/trees/phystree.py
+++ b/src/neat/trees/phystree.py
@@ -557,6 +557,7 @@ def set_physiology(self, c_m_distr, r_a_distr, g_s_distr=None, node_arg=None):
                 if g_s_distr is not None
                 else 0.0
             )
+            assert int(np.sign(g_s)) != -1
             node.set_physiology(c_m, r_a, g_s)
 
     @comptree_removal_decorator
@@ -588,6 +589,7 @@ def set_leak_current(self, g_l_distr, e_l_distr, node_arg=None):
         for node in self.convert_node_arg_to_nodes(node_arg):
             g_l = self._distr2Float(g_l_distr, node, argname="`g_l_distr`")
             e_l = self._distr2Float(e_l_distr, node, argname="`e_l_distr`")
+            assert int(np.sign(g_l)) != -1
             node._add_current("L", g_l, e_l)
 
     @comptree_removal_decorator
@@ -631,6 +633,7 @@ def add_channel_current(self, channel, g_max_distr, e_rev_distr, node_arg=None):
         for node in self.convert_node_arg_to_nodes(node_arg):
             g_max = self._distr2Float(g_max_distr, node, argname="`g_max_distr`")
             e_rev = self._distr2Float(e_rev_distr, node, argname="`e_rev_distr`")
+            assert int(np.sign(g_max)) != -1
             node._add_current(channel_name, g_max, e_rev)
 
     def get_channels_in_tree(self):
diff --git a/tests/test_phystree.py b/tests/test_phystree.py
index 7bc48e50..deb3f6ba 100755
--- a/tests/test_phystree.py
+++ b/tests/test_phystree.py
@@ -204,6 +204,9 @@ def test_physiology_setting(self):
         # as wrong type
         with pytest.raises(TypeError):
             self.tree.set_leak_current([])
+        # wrong sign
+        with pytest.raises(AssertionError):
+            self.tree.set_leak_current(e_l, g_l)
 
         # gmax as potential as float
         e_rev = 100.0
@@ -233,6 +236,9 @@ def test_physiology_setting(self):
         # check if error is thrown if an ionchannel is not give
         with pytest.raises(IOError):
             self.tree.add_channel_current("test_channel2", g_max, e_rev)
+        # check if error is thrown if an ionchannel is not give
+        with pytest.raises(AssertionError):
+            self.tree.add_channel_current(channel, -10.0, e_rev)
 
     def test_membrane_functions(self):
         self.load_tree()