diff --git a/python/tools/prepare_build_environment_linux.sh b/python/tools/prepare_build_environment_linux.sh
index b47b865f5..61ac171a3 100755
--- a/python/tools/prepare_build_environment_linux.sh
+++ b/python/tools/prepare_build_environment_linux.sh
@@ -20,7 +20,7 @@ if [ "$CIBW_ARCHS" == "aarch64" ]; then
 
 else
     # Install CUDA 12.2:
-    yum-config-manager --add-repo https://developer.download.nvidia.com/compute/cuda/repos/rhel7/x86_64/cuda-rhel7.repo
+    yum-config-manager --add-repo https://developer.download.nvidia.com/compute/cuda/repos/rhel8/x86_64/cuda-rhel8.repo
     # error mirrorlist.centos.org doesn't exists anymore.
     sed -i s/mirror.centos.org/vault.centos.org/g /etc/yum.repos.d/*.repo
     sed -i s/^#.*baseurl=http/baseurl=http/g /etc/yum.repos.d/*.repo
@@ -29,7 +29,7 @@ else
         cuda-nvcc-12-2-12.2.140-1 \
         cuda-cudart-devel-12-2-12.2.140-1 \
         libcurand-devel-12-2-10.3.3.141-1 \
-        libcudnn8-devel-8.9.7.29-1.cuda12.2 \
+        libcudnn9-devel-cuda-12-9.1.0.70-1 \
         libcublas-devel-12-2-12.2.5.6-1 \
         libnccl-devel-2.19.3-1+cuda12.2
     ln -s cuda-12.2 /usr/local/cuda
diff --git a/python/tools/prepare_build_environment_windows.sh b/python/tools/prepare_build_environment_windows.sh
index 1a4d76eeb..f72aad035 100755
--- a/python/tools/prepare_build_environment_windows.sh
+++ b/python/tools/prepare_build_environment_windows.sh
@@ -8,10 +8,24 @@ curl -L -nv -o cuda.exe https://developer.download.nvidia.com/compute/cuda/12.2.
 ./cuda.exe -s nvcc_12.2 cudart_12.2 cublas_dev_12.2 curand_dev_12.2
 rm cuda.exe
 
-CUDNN_ROOT="C:/Program Files/NVIDIA/CUDNN/v8.8"
-curl -L -nv -o cudnn.exe https://developer.download.nvidia.com/compute/redist/cudnn/v8.8.0/local_installers/12.0/cudnn_8.8.0.121_windows.exe
+CUDNN_ROOT="C:/Program Files/NVIDIA/CUDNN/v9.1"
+curl -L -nv -o cudnn.exe https://developer.download.nvidia.com/compute/cudnn/9.1.0/local_installers/cudnn_9.1.0_windows.exe
 ./cudnn.exe -s
 sleep 10
+# Remove 11.8 folders
+rm -rf "$CUDNN_ROOT/bin/11.8"
+rm -rf "$CUDNN_ROOT/lib/11.8"
+rm -rf "$CUDNN_ROOT/include/11.8"
+
+# Move contents of 12.4 to parent directories
+mv "$CUDNN_ROOT/bin/12.4/"* "$CUDNN_ROOT/bin/"
+mv "$CUDNN_ROOT/lib/12.4/"* "$CUDNN_ROOT/lib/"
+mv "$CUDNN_ROOT/include/12.4/"* "$CUDNN_ROOT/include/"
+
+# Remove empty 12.4 folders
+rmdir "$CUDNN_ROOT/bin/12.4"
+rmdir "$CUDNN_ROOT/lib/12.4"
+rmdir "$CUDNN_ROOT/include/12.4"
 cp -r "$CUDNN_ROOT"/* "$CUDA_ROOT"
 rm cudnn.exe
 
@@ -40,4 +54,4 @@ rm -r build
 cp README.md python/
 cp $CTRANSLATE2_ROOT/bin/ctranslate2.dll python/ctranslate2/
 cp "C:/Program Files (x86)/Intel/oneAPI/compiler/latest/windows/redist/intel64_win/compiler/libiomp5md.dll" python/ctranslate2/
-cp "$CUDA_ROOT/bin/cudnn64_8.dll" python/ctranslate2/
+cp "$CUDA_ROOT/bin/cudnn64_9.dll" python/ctranslate2/