diff --git a/src/osmo_gsm_tester/suite.py b/src/osmo_gsm_tester/suite.py
index 44aabbd..76cd248 100644
--- a/src/osmo_gsm_tester/suite.py
+++ b/src/osmo_gsm_tester/suite.py
@@ -70,6 +70,7 @@
     resources_pool = None
     reserved_resources = None
     objects_to_clean_up = None
+    test_import_modules_to_clean_up = []
     _resource_requirements = None
     _config = None
     _processes = None
@@ -102,6 +103,27 @@
             except Exception:
                 log.log_exn()
 
+    def test_import_modules_register_for_cleanup(self, mod):
+        '''
+        Tests are required to call this API for any module loaded from its own
+        lib subdir, because they are loaded in the global namespace. Otherwise
+        later tests importing modules with the same name will re-use an already
+        loaded module.
+        '''
+        if mod not in self.test_import_modules_to_clean_up:
+            self.dbg('registering module %r for cleanup' % mod)
+            self.test_import_modules_to_clean_up.append(mod)
+
+    def test_import_modules_cleanup(self):
+        while self.test_import_modules_to_clean_up:
+            mod = self.test_import_modules_to_clean_up.pop()
+            try:
+                self.dbg('Cleaning up module %r' % mod)
+                del sys.modules[mod.__name__]
+                del mod
+            except Exception:
+                log.log_exn()
+
     def mark_start(self):
         self.start_timestamp = time.time()
         self.duration = 0
@@ -179,6 +201,7 @@
             self.objects_cleanup()
             self.free_resources()
             MainLoop.unregister_poll_func(self.poll)
+            self.test_import_modules_cleanup()
             util.import_path_remove(suite_libdir)
             self.duration = time.time() - self.start_timestamp
 
diff --git a/suites/dyn_ts_ipa/mo_mt_call_dyn_ipa.py b/suites/dyn_ts_ipa/mo_mt_call_dyn_ipa.py
index f1771b9..82e357c 100755
--- a/suites/dyn_ts_ipa/mo_mt_call_dyn_ipa.py
+++ b/suites/dyn_ts_ipa/mo_mt_call_dyn_ipa.py
@@ -1,6 +1,8 @@
 #!/usr/bin/env python3
 from osmo_gsm_tester.testenv import *
 
+import testlib
+suite.test_import_modules_register_for_cleanup(testlib)
 from testlib import call_test_setup_run
 
 def my_bts_setup(bts):
diff --git a/suites/dyn_ts_osmo/mo_mt_call_dyn_osmo.py b/suites/dyn_ts_osmo/mo_mt_call_dyn_osmo.py
index c7fe0c3..1424da8 100755
--- a/suites/dyn_ts_osmo/mo_mt_call_dyn_osmo.py
+++ b/suites/dyn_ts_osmo/mo_mt_call_dyn_osmo.py
@@ -1,6 +1,8 @@
 #!/usr/bin/env python3
 from osmo_gsm_tester.testenv import *
 
+import testlib
+suite.test_import_modules_register_for_cleanup(testlib)
 from testlib import call_test_setup_run
 
 def my_bts_setup(bts):
diff --git a/suites/voice/mo_mt_call_tchf.py b/suites/voice/mo_mt_call_tchf.py
index a640a97..af55dfd 100755
--- a/suites/voice/mo_mt_call_tchf.py
+++ b/suites/voice/mo_mt_call_tchf.py
@@ -1,6 +1,8 @@
 #!/usr/bin/env python3
 from osmo_gsm_tester.testenv import *
 
+import testlib
+suite.test_import_modules_register_for_cleanup(testlib)
 from testlib import call_test_setup_run
 
 def my_bts_setup(bts):
diff --git a/suites/voice/mo_mt_call_tchh.py b/suites/voice/mo_mt_call_tchh.py
index e6f6b98..43d0760 100755
--- a/suites/voice/mo_mt_call_tchh.py
+++ b/suites/voice/mo_mt_call_tchh.py
@@ -1,6 +1,8 @@
 #!/usr/bin/env python3
 from osmo_gsm_tester.testenv import *
 
+import testlib
+suite.test_import_modules_register_for_cleanup(testlib)
 from testlib import call_test_setup_run
 
 def my_bts_setup(bts):