diff --git a/Tests/test_file_bufrstub.py b/Tests/test_file_bufrstub.py
index 362578c56..1fb0a0daf 100644
--- a/Tests/test_file_bufrstub.py
+++ b/Tests/test_file_bufrstub.py
@@ -51,6 +51,9 @@ def test_save(tmp_path: Path) -> None:
 
 
 def test_handler(tmp_path: Path) -> None:
+    if BufrStubImagePlugin._handler is not None:
+        return
+
     class TestHandler(ImageFile.StubHandler):
         opened = False
         loaded = False
diff --git a/Tests/test_file_gribstub.py b/Tests/test_file_gribstub.py
index 960e5f4be..ce01aa1d3 100644
--- a/Tests/test_file_gribstub.py
+++ b/Tests/test_file_gribstub.py
@@ -51,6 +51,9 @@ def test_save(tmp_path: Path) -> None:
 
 
 def test_handler(tmp_path: Path) -> None:
+    if GribStubImagePlugin._handler is not None:
+        return
+
     class TestHandler(ImageFile.StubHandler):
         opened = False
         loaded = False
diff --git a/Tests/test_file_hdf5stub.py b/Tests/test_file_hdf5stub.py
index e4f09a09c..126522ed8 100644
--- a/Tests/test_file_hdf5stub.py
+++ b/Tests/test_file_hdf5stub.py
@@ -53,6 +53,9 @@ def test_save() -> None:
 
 
 def test_handler(tmp_path: Path) -> None:
+    if Hdf5StubImagePlugin._handler is not None:
+        return
+
     class TestHandler(ImageFile.StubHandler):
         opened = False
         loaded = False
diff --git a/Tests/test_file_wmf.py b/Tests/test_file_wmf.py
index dcf5f000f..00394114c 100644
--- a/Tests/test_file_wmf.py
+++ b/Tests/test_file_wmf.py
@@ -53,15 +53,19 @@ def test_render() -> None:
             assert_image_equal_tofile(im, "Tests/images/drawing.emf")
 
 
+class TestHandler(ImageFile.StubHandler):
+    methodCalled = False
+
+    def load(self, im: ImageFile.StubImageFile) -> Image.Image:
+        return Image.new("RGB", (1, 1))
+
+    def save(self, im: Image.Image, fp: IO[bytes], filename: str) -> None:
+        self.methodCalled = True
+
+
 def test_register_handler(tmp_path: Path) -> None:
-    class TestHandler(ImageFile.StubHandler):
-        methodCalled = False
-
-        def load(self, im: ImageFile.StubImageFile) -> Image.Image:
-            return Image.new("RGB", (1, 1))
-
-        def save(self, im: Image.Image, fp: IO[bytes], filename: str) -> None:
-            self.methodCalled = True
+    if isinstance(WmfImagePlugin._handler, TestHandler):
+        return
 
     handler = TestHandler()
     original_handler = WmfImagePlugin._handler