diff --git a/calibre-plugin/gui_main.py b/calibre-plugin/gui_main.py
index 998847d..c7a259a 100644
--- a/calibre-plugin/gui_main.py
+++ b/calibre-plugin/gui_main.py
@@ -9,7 +9,13 @@
 
 from calibre.gui2.actions import InterfaceAction
 from calibre.gui2.actions import menu_action_unique_name
-from PyQt5.QtGui import QMenu, QToolButton
+try: 
+    from PyQt5.QtGui import QMenu, QToolButton
+except ImportError:
+    try: 
+        from PyQt5.QtWidgets import QMenu, QToolButton
+    except ImportError:
+        from PyQt4.Qt import QMenu, QToolButton
 
 
 #@@CALIBRE_COMPAT_CODE@@
@@ -61,13 +67,19 @@ class ActualACSMInputGUIExtension(InterfaceAction):
     # Text, icon, tooltip, keyboard shortcut
 
     def genesis(self): 
-        print("Genesis!")
+        print("ACSM Input: GUI Plugin Genesis!")
         self.menu = QMenu(self.gui)
 
         self.rebuild_menus()
 
         self.qaction.setMenu(self.menu)
-        icon = get_icons('acsm_logo_2.png', "ACSM Input Plugin")
+        try:
+            # Py3 
+            icon = get_icons('acsm_logo_2.png', "ACSM Input Plugin")
+        except TypeError:
+            # Py2
+            icon = get_icons('acsm_logo_2.png')
+
         self.qaction.setIcon(icon)
         #self.qaction.triggered.connect(self.trigger_config_dialog)
 
diff --git a/calibre-plugin/gui_main_wrapper.py b/calibre-plugin/gui_main_wrapper.py
index 0a1a89d..e3b1400 100644
--- a/calibre-plugin/gui_main_wrapper.py
+++ b/calibre-plugin/gui_main_wrapper.py
@@ -5,7 +5,10 @@
 #
 
 from calibre.customize import InterfaceActionBase        # type: ignore
-from calibre.customize import PluginInstallationType
+try: 
+    from calibre.customize import PluginInstallationType
+except:
+    pass
 
 
 
@@ -25,8 +28,12 @@ class ACSMInputGUIExtension(InterfaceActionBase):
     type = "File type"
     # Just so that the GUI extension shows up at the same place as the actual ACSM Input plugin.
 
-    installation_type = PluginInstallationType.EXTERNAL
-    # Mark this as user-installed so it shows up in the plugin list by default. 
+    try: 
+        installation_type = PluginInstallationType.EXTERNAL
+        # Mark this as user-installed so it shows up in the plugin list by default. 
+    except: 
+        # Setting the Installation type doesn't always work on Calibre 4 and below.
+        pass
 
     actual_plugin = "calibre_plugins.deacsm.gui_main:ActualACSMInputGUIExtension"
 
diff --git a/migration_plugin/__init__.py b/migration_plugin/__init__.py
index bfa5a77..522007c 100644
--- a/migration_plugin/__init__.py
+++ b/migration_plugin/__init__.py
@@ -10,7 +10,10 @@
 
 
 from calibre.customize import InterfaceActionBase        # type: ignore
-from calibre.customize import PluginInstallationType
+try: 
+    from calibre.customize import PluginInstallationType
+except:
+    pass
 
 
 class DeACSMMigrationPlugin(InterfaceActionBase):
@@ -28,8 +31,12 @@ class DeACSMMigrationPlugin(InterfaceActionBase):
     type = "File type"
     # Just so that the GUI extension shows up at the same place as the actual ACSM Input plugin.
 
-    installation_type = PluginInstallationType.EXTERNAL
-    # Mark this as user-installed so it shows up in the plugin list by default. 
+    try: 
+        installation_type = PluginInstallationType.EXTERNAL
+        # Mark this as user-installed so it shows up in the plugin list by default. 
+    except: 
+        # Setting the Installation type doesn't always work on Calibre 4 and below.
+        pass
 
     actual_plugin = "calibre_plugins.deacsm.migration:ActualMigrationPlugin"