diff --git a/.ci/install.sh b/.ci/install.sh
index a8e82fa49..77dccaa4a 100755
--- a/.ci/install.sh
+++ b/.ci/install.sh
@@ -31,7 +31,8 @@ python3 -m pip install -U pytest
 python3 -m pip install -U pytest-cov
 python3 -m pip install pyroma
 python3 -m pip install test-image-results
-python3 -m pip install numpy
+# TODO Remove condition when numpy supports 3.10
+if ! [ "$GHA_PYTHON_VERSION" == "3.10-dev" ]; then python3 -m pip install numpy ; fi
 
 # TODO Remove when 3.8 / 3.9 / PyPy3 includes setuptools 49.3.2+:
 if [ "$GHA_PYTHON_VERSION" == "3.8" ]; then python3 -m pip install -U "setuptools>=49.3.2" ; fi
diff --git a/.github/workflows/macos-install.sh b/.github/workflows/macos-install.sh
index 473412d3b..fb8869c7d 100755
--- a/.github/workflows/macos-install.sh
+++ b/.github/workflows/macos-install.sh
@@ -13,7 +13,8 @@ python3 -m pip install pyroma
 python3 -m pip install test-image-results
 
 echo -e "[openblas]\nlibraries = openblas\nlibrary_dirs = /usr/local/opt/openblas/lib" >> ~/.numpy-site.cfg
-python3 -m pip install numpy
+# TODO Remove condition when numpy supports 3.10
+if ! [ "$GHA_PYTHON_VERSION" == "3.10-dev" ]; then python3 -m pip install numpy ; fi
 
 # TODO Remove when 3.8 / 3.9 includes setuptools 49.3.2+:
 if [ "$GHA_PYTHON_VERSION" == "3.8" ]; then python3 -m pip install -U "setuptools>=49.3.2" ; fi
diff --git a/.github/workflows/test-windows.yml b/.github/workflows/test-windows.yml
index a7fb2bdbc..4d3619edb 100644
--- a/.github/workflows/test-windows.yml
+++ b/.github/workflows/test-windows.yml
@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.6", "3.7", "3.8", "3.9", "pypy3"]
+        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10-dev", "pypy3"]
         architecture: ["x86", "x64"]
         include:
           - architecture: "x86"
@@ -182,14 +182,16 @@ jobs:
 
     - name: Build wheel
       id: wheel
-      if: "github.event_name == 'push'"
+      # Skip wheels on 3.10 due to https://github.com/pypa/wheel/issues/354
+      if: "github.event_name == 'push' && !contains(matrix.python-version, '3.10')"
       run: |
         for /f "tokens=3 delims=/" %%a in ("${{ github.ref }}") do echo ::set-output name=dist::dist-%%a
         winbuild\\build\\build_pillow.cmd --disable-imagequant bdist_wheel
       shell: cmd
 
     - uses: actions/upload-artifact@v2
-      if: "github.event_name == 'push'"
+      # Skip wheels on 3.10 due to https://github.com/pypa/wheel/issues/354
+      if: "github.event_name == 'push' && !contains(matrix.python-version, '3.10')"
       with:
         name: ${{ steps.wheel.outputs.dist }}
         path: dist\*.whl
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 1fc8a09cb..3da945f39 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -14,6 +14,7 @@ jobs:
         ]
         python-version: [
           "pypy3",
+          "3.10-dev",
           "3.9",
           "3.8",
           "3.7",
diff --git a/src/display.c b/src/display.c
index 2eb4a5855..c95844bbc 100644
--- a/src/display.c
+++ b/src/display.c
@@ -22,7 +22,7 @@
  * See the README file for information on usage and redistribution.
  */
 
-
+#define PY_SSIZE_T_CLEAN
 #include "Python.h"
 
 #include "libImaging/Imaging.h"
@@ -196,7 +196,7 @@ static PyObject*
 _frombytes(ImagingDisplayObject* display, PyObject* args)
 {
     char* ptr;
-    int bytes;
+    Py_ssize_t bytes;
 
     if (!PyArg_ParseTuple(args, "y#:frombytes", &ptr, &bytes)) {
         return NULL;
@@ -777,7 +777,7 @@ PyImaging_DrawWmf(PyObject* self, PyObject* args)
     char* ptr;
 
     char* data;
-    int datasize;
+    Py_ssize_t datasize;
     int width, height;
     int x0, y0, x1, y1;
     if (!PyArg_ParseTuple(args, "y#(ii)(iiii):_load", &data, &datasize,