diff --git a/matplotlib_scalebar/scalebar.py b/matplotlib_scalebar/scalebar.py
index d4c7917..f89eb04 100644
--- a/matplotlib_scalebar/scalebar.py
+++ b/matplotlib_scalebar/scalebar.py
@@ -111,11 +111,15 @@ def _validate_legend_loc(loc):
     }
 )
 
+
+_all_deprecated = getattr(matplotlib, "_all_deprecated", {})
+
+
 # Recreate the validate function
 matplotlib.rcParams.validate = dict(
     (key, converter)
     for key, (default, converter) in defaultParams.items()
-    if key not in matplotlib._all_deprecated
+    if key not in _all_deprecated
 )
 
 # Dimension lookup
diff --git a/setup.py b/setup.py
index 450c0a4..b188976 100644
--- a/setup.py
+++ b/setup.py
@@ -35,10 +35,15 @@
         "License :: OSI Approved :: MIT License",
         "Operating System :: OS Independent",
         "Programming Language :: Python :: 3",
+        "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
+        "Programming Language :: Python :: 3.10",
         "Topic :: Scientific/Engineering :: Visualization",
     ],
     packages=find_packages(),
     package_data={},
+    python_requires='~=3.7',
     install_requires=["matplotlib"],
     zip_safe=True,
     cmdclass=versioneer.get_cmdclass(),