diff --git a/tests/TestThemes.py b/tests/TestThemes.py
new file mode 100644
index 0000000000..a84d94298c
--- /dev/null
+++ b/tests/TestThemes.py
@@ -0,0 +1,33 @@
+# Copyright (c) 2021 Ultimaker B.V.
+# Cura is released under the terms of the LGPLv3 or higher.
+
+import json  # To parse the deprecated icons files.
+import os  # To find the theme folders.
+import pytest
+
+theme_base = os.path.join(os.path.split(__file__)[0], "..", "resources", "themes")
+theme_paths = [os.path.join(theme_base, theme_folder) for theme_folder in os.listdir(theme_base) if os.path.isdir(os.path.join(theme_base, theme_folder))]
+
+@pytest.mark.parametrize("theme_path", theme_paths)
+def test_deprecatedIconsExist(theme_path: str) -> None:
+    icons_folder = os.path.join(theme_path, "icons")
+    deprecated_icons_file = os.path.join(icons_folder, "deprecated_icons.json")
+    if not os.path.exists(deprecated_icons_file):
+        return  # No deprecated icons file, there is nothing to go wrong.
+
+    # Find out which icons exist in this theme file.
+    existing_icons = {}
+    for size in [subfolder for subfolder in os.listdir(icons_folder) if os.path.isdir(os.path.join(icons_folder, subfolder))]:
+        existing_icons[size] = set(os.path.splitext(fname)[0] for fname in os.listdir(os.path.join(icons_folder, size)))
+
+    with open(deprecated_icons_file) as f:
+        deprecated_icons = json.load(f)
+
+    for entry in deprecated_icons.values():
+        assert "new_icon" in entry  # For each deprecated icon we must know which icon replaced it.
+        new_icon = entry["new_icon"]
+        assert "size" in entry
+        size = entry["size"]
+
+        assert size in existing_icons  # The replacement icon must have a size that exists.
+        assert new_icon in existing_icons[size]  # The new icon must exist for that size.