diff --git a/tests/fprintd.py b/tests/fprintd.py
index a1fef1c..8d8fe6e 100644
--- a/tests/fprintd.py
+++ b/tests/fprintd.py
@@ -592,10 +592,10 @@ class FPrintdTest(dbusmock.DBusTestCase):
             proc = self.gdbus_device_method_call_process(method, args)
             proc.wait(timeout=5)
             if proc.returncode != 0:
-                raise GLib.GError(proc.stdout.read())
+                raise GLib.GError(proc.stdout.read().decode())
             return proc.stdout.read()
         except subprocess.TimeoutExpired as e:
-            raise GLib.GError(e.output)
+            raise GLib.GError(e.output.decode())
 
 
 class FPrintdVirtualImageDeviceBaseTests(FPrintdTest):
@@ -2990,7 +2990,7 @@ class FPrindConcurrentPolkitRequestsTest(FPrintdVirtualStorageDeviceBaseTest):
 
         gdbus.wait()
         with self.assertFprintError('AlreadyInUse'):
-            raise GLib.GError(gdbus.stdout.read())
+            raise GLib.GError(gdbus.stdout.read().decode())
 
         self.device.Release()
 
@@ -3032,7 +3032,7 @@ class FPrindConcurrentPolkitRequestsTest(FPrintdVirtualStorageDeviceBaseTest):
 
         gdbus.wait()
         with self.assertFprintError('AlreadyInUse'):
-            raise GLib.GError(gdbus.stdout.read())
+            raise GLib.GError(gdbus.stdout.read().decode())
 
         self.device.Release()