diff --git a/docker/Dockerfile.template b/docker/Dockerfile.template
index 2b48eee7..864660f7 100644
--- a/docker/Dockerfile.template
+++ b/docker/Dockerfile.template
@@ -11,7 +11,12 @@ RUN for V in ${PLATFORMS}; do \
         mkdir "/opt/${PLATFORM}" && \
         tar -xaf "/cache/ds.${PLATFORM}-${TOOLKIT_VER}.dev.txz" -C "/opt/${PLATFORM}" --strip-components=10 \
           "usr/local/x86_64-pc-linux-gnu/x86_64-pc-linux-gnu/sys-root/usr/lib/modules/DSM-7.0/build" && \
-        echo -e "${PLATFORM}\t${KVER}" >> /opt/platforms; \
+        echo -e "${PLATFORM}\t${KVER}" >> /opt/platforms && \
+        if [ ! -d "/opt/linux-${KVER}" ]; then \
+          mkdir "/opt/linux-${KVER}" && \
+          echo "Extracting linux-${KVER}.tar.xz" && \
+          tar -xaf "/cache/linux-${KVER}.tar.xz" -C "/opt/linux-${KVER}" --strip-components=1; \
+        fi; \
       done; \
     done
 
@@ -22,7 +27,7 @@ ENV SHELL=/bin/bash \
 
 RUN apt update --yes && \
     apt install --yes --no-install-recommends --no-install-suggests \
-      build-essential nano make ncurses-dev && \
+      build-essential nano make ncurses-dev bc libssl-dev && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/*
 
diff --git a/docker/build.sh b/docker/build.sh
index 995765b1..386def5d 100755
--- a/docker/build.sh
+++ b/docker/build.sh
@@ -20,6 +20,7 @@ done <../PLATFORMS
 mkdir -p cache
 TOOLKIT_VER="7.0"
 for PLATFORM in ${!PLATFORMS[@]}; do
+  KVER="${PLATFORMS[${PLATFORM}]}"
   echo -n "Checking cache/ds.${PLATFORM}-${TOOLKIT_VER}.dev.txz... "
   if [ ! -f "cache/ds.${PLATFORM}-${TOOLKIT_VER}.dev.txz" ]; then
     URL="https://global.download.synology.com/download/ToolChain/toolkit/${TOOLKIT_VER}/${PLATFORM}/ds.${PLATFORM}-${TOOLKIT_VER}.dev.txz"
@@ -28,6 +29,14 @@ for PLATFORM in ${!PLATFORMS[@]}; do
   else
     echo "OK"
   fi
+  echo -n "Checking cache/linux-${KVER}.tar.xz... "
+  if [ ! -f "cache/linux-${KVER}.tar.xz" ]; then
+    URL="https://cdn.kernel.org/pub/linux/kernel/v${KVER:0:1}.x/linux-${KVER}.tar.xz"
+    echo "Downloading ${URL}"
+    curl -L "${URL}" -o "cache/linux-${KVER}.tar.xz"
+  else
+    echo "OK"
+  fi
 done
 
 # Generate Dockerfile