diff --git a/buildingspy/CHANGES.txt b/buildingspy/CHANGES.txt
index 9b48d7c6..b77e0464 100644
--- a/buildingspy/CHANGES.txt
+++ b/buildingspy/CHANGES.txt
@@ -3,7 +3,8 @@ BuildingsPy Changelog
 
 Version 5.2.1, ...
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
+- In buildingspy/development/regressiontest.py, changed MODELICAPATH on Windows to use ';' instead of ':'
+  (https://github.com/lbl-srg/BuildingsPy/issues/609)
 - Updated pyfunnel to version 2.0.1 to fix plotting issues.
   With this change, Python 2 is no longer supported.
   (https://github.com/lbl-srg/BuildingsPy/issues/599)
diff --git a/buildingspy/__init__.py b/buildingspy/__init__.py
index ffa7a56b..4bd90679 100644
--- a/buildingspy/__init__.py
+++ b/buildingspy/__init__.py
@@ -9,3 +9,14 @@
 version_path = os.path.abspath(os.path.join(os.path.dirname(__file__), 'VERSION'))
 with open(version_path) as f:
     __version__ = f.read().strip()
+
+class BuildingsPy:
+    """Class with static methods that are used in various modules.
+
+    """
+    @staticmethod
+    def getModelicaPathSeparator():
+        ''' Returns the `MODELICAPATH` separator, which is `;` on Windows and `:` otherwise.
+        '''
+        import platform
+        return ';' if platform.system() == 'Windows' else ':'
diff --git a/buildingspy/development/regressiontest.py b/buildingspy/development/regressiontest.py
index 6d42a587..ee909477 100644
--- a/buildingspy/development/regressiontest.py
+++ b/buildingspy/development/regressiontest.py
@@ -3673,6 +3673,7 @@ def _write_python_runscripts(self, iPro, tra_data_pro):
         import inspect
         import buildingspy.development.regressiontest as r
         import jinja2
+        from buildingspy import BuildingsPy
 
         directory = self._temDir[iPro]
 
@@ -3721,10 +3722,7 @@ def _getStartStopTime(key, dat):
                 model_modifier = ""
 
                 # Get delimiter for MODELICAPATH
-                if os.name == 'nt':
-                    col = ";"
-                else:
-                    col = ":"
+                col = BuildingsPy.getModelicaPathSeparator()
 
                 # Get the MODELICAPATH
                 if 'MODELICAPATH' in os.environ:
diff --git a/buildingspy/simulate/OpenModelica.py b/buildingspy/simulate/OpenModelica.py
index f76afc94..e66dcad1 100644
--- a/buildingspy/simulate/OpenModelica.py
+++ b/buildingspy/simulate/OpenModelica.py
@@ -192,6 +192,7 @@ def _translate_and_simulate(self, simulate):
 #        import datetime
 
         from sys import platform
+        from buildingspy import BuildingsPy
 
         # Delete output files
         self.deleteOutputFiles()
@@ -211,10 +212,7 @@ def _translate_and_simulate(self, simulate):
         file_name = "{}.py".format(self.modelName.replace(".", "_"))
 
         # Get delimiter for MODELICAPATH
-        if os.name == 'nt':
-            col = ";"
-        else:
-            col = ":"
+        col = BuildingsPy.getModelicaPathSeparator()
 
         # Get the MODELICAPATH
         if 'MODELICAPATH' in os.environ:
diff --git a/buildingspy/simulate/base_simulator.py b/buildingspy/simulate/base_simulator.py
index 01068901..8aecf127 100644
--- a/buildingspy/simulate/base_simulator.py
+++ b/buildingspy/simulate/base_simulator.py
@@ -548,17 +548,15 @@ def prependToModelicaPath(env, path):
             >>> env = os.environ.copy()
             >>> env = s.prependToModelicaPath(env, os.getcwd())
 
-         '''
+        '''
+        from buildingspy import BuildingsPy
+
         if path is None:
             return env
         else:
             if 'MODELICAPATH' in env:
-                import platform
-
-                if platform.system() == 'Windows':
-                    env['MODELICAPATH'] = ";".join([path, env['MODELICAPATH']])
-                else:
-                    env['MODELICAPATH'] = ":".join([path, env['MODELICAPATH']])
+                env['MODELICAPATH'] = BuildingsPy.getModelicaPathSeparator().join(
+                    [path, env['MODELICAPATH']])
             else:
                 env['MODELICAPATH'] = path
             return env