diff --git a/changes/2485.bugfix.rst b/changes/2485.bugfix.rst
new file mode 100644
index 0000000000..ddf0403402
--- /dev/null
+++ b/changes/2485.bugfix.rst
@@ -0,0 +1 @@
+Exception raised by ProgressBar on Windows regarding transparent background has been resolved.
diff --git a/testbed/tests/widgets/test_progressbar.py b/testbed/tests/widgets/test_progressbar.py
index a08e005b16..2f6372ee7d 100644
--- a/testbed/tests/widgets/test_progressbar.py
+++ b/testbed/tests/widgets/test_progressbar.py
@@ -3,6 +3,7 @@
 import toga
 
 from .properties import (  # noqa: F401
+    test_background_color_transparent,
     test_enable_noop,
     test_flex_horizontal_widget_size,
 )
diff --git a/winforms/src/toga_winforms/widgets/progressbar.py b/winforms/src/toga_winforms/widgets/progressbar.py
index 40efc73221..e1a8aa85f7 100644
--- a/winforms/src/toga_winforms/widgets/progressbar.py
+++ b/winforms/src/toga_winforms/widgets/progressbar.py
@@ -21,6 +21,7 @@
 
 class ProgressBar(Widget):
     TOGA_SCALE = 1000
+    _background_supports_alpha = False
 
     def create(self):
         self.native = WinForms.ProgressBar()
diff --git a/winforms/tests_backend/widgets/progressbar.py b/winforms/tests_backend/widgets/progressbar.py
index 76b43be525..4aa5a3c2c5 100644
--- a/winforms/tests_backend/widgets/progressbar.py
+++ b/winforms/tests_backend/widgets/progressbar.py
@@ -5,6 +5,7 @@
 
 class ProgressBarProbe(SimpleProbe):
     native_class = System.Windows.Forms.ProgressBar
+    background_supports_alpha = False
 
     @property
     def is_determinate(self):