diff --git a/src/modules/dummypython/main.py b/src/modules/dummypython/main.py
index c173c294d..e0153b881 100644
--- a/src/modules/dummypython/main.py
+++ b/src/modules/dummypython/main.py
@@ -41,5 +41,4 @@ def run():
                                + str( libcalamares.globalStorage.value( "item3" ) ) + "\n"
 
     libcalamares.job.setprogress( 0.1 )
-    return accumulator
-
+    return ( "", accumulator )
diff --git a/src/modules/grub/main.py b/src/modules/grub/main.py
index d735f0681..affbc8bea 100644
--- a/src/modules/grub/main.py
+++ b/src/modules/grub/main.py
@@ -77,4 +77,4 @@ def run():
         installGrub( rootMountPoint, bootLoader )
     finally:
         umountPartitions( rootMountPoint, extraMounts )
-    return "All done"
+    return None
diff --git a/src/modules/mount/main.py b/src/modules/mount/main.py
index 8fc928f5b..783b69bde 100644
--- a/src/modules/mount/main.py
+++ b/src/modules/mount/main.py
@@ -61,4 +61,4 @@ def run():
     mountPartitions( rootMountPoint, libcalamares.globalStorage.value( "partitions" ) )
 
     libcalamares.globalStorage.insert( "rootMountPoint", rootMountPoint )
-    return "All done, mounted at {}".format( rootMountPoint )
+    return None
diff --git a/src/modules/umount/main.py b/src/modules/umount/main.py
index 5817a95b5..34b7349db 100644
--- a/src/modules/umount/main.py
+++ b/src/modules/umount/main.py
@@ -35,9 +35,9 @@ def listMounts( rootMountPoint ):
 def run():
     rootMountPoint = libcalamares.globalStorage.value( "rootMountPoint" )
     if not rootMountPoint:
-        return "GlobalStorage does not contain a \"rootMountPoint\" key, doing nothing"
+        return ( "No mount point for root partition in GlobalStorage", "GlobalStorage does not contain a \"rootMountPoint\" key, doing nothing" )
     if not os.path.exists( rootMountPoint ):
-        return "GlobalStorage[\"rootMountPoint\"] is \"{}\", which does not exist, doing nothing".format( rootMountPoint )
+        return ( "Bad mount point for root partition in GlobalStorage", "GlobalStorage[\"rootMountPoint\"] is \"{}\", which does not exist, doing nothing".format( rootMountPoint ) )
 
     lst = listMounts( rootMountPoint )
     # Sort the list by mount point in decreasing order. This way we can be sure
@@ -48,4 +48,4 @@ def run():
         subprocess.check_call( [ "umount", mountPoint ] )
 
     os.rmdir( rootMountPoint )
-    return "All done"
+    return None
diff --git a/src/modules/unsquashfs/main.py b/src/modules/unsquashfs/main.py
index 8585baf2d..fc9416cae 100644
--- a/src/modules/unsquashfs/main.py
+++ b/src/modules/unsquashfs/main.py
@@ -106,7 +106,12 @@ def run():
     #           destination: ""
 
     rootMountPoint = globalStorage.value( "rootMountPoint" )
-
+    if not rootMountPoint:
+        return ( "No mount point for root partition in GlobalStorage",
+                 "GlobalStorage does not contain a \"rootMountPoint\" key, doing nothing" )
+    if not os.path.exists( rootMountPoint ):
+        return ( "Bad mount point for root partition in GlobalStorage",
+                 "GlobalStorage[\"rootMountPoint\"] is \"{}\", which does not exist, doing nothing".format( rootMountPoint ) )
     unpack = list()
 
     for entry in job.configuration[ "unpack" ]:
@@ -114,7 +119,8 @@ def run():
         destination = os.path.abspath( os.path.join( rootMountPoint, entry[ "destination" ] ) )
 
         if not os.path.isfile( source ) or not os.path.isdir( destination ):
-            return "Error: bad source or destination"
+            return ( "Bad source or destination",
+                     "source=\"{}\"\ndestination=\"{}\"".format( source, destination ) )
 
         unpack.append( UnpackEntry( source, destination ) )