diff --git a/script/makeinstaller-assets.json b/script/makeinstaller-assets.json
new file mode 100644
index 00000000..a180a622
--- /dev/null
+++ b/script/makeinstaller-assets.json
@@ -0,0 +1,52 @@
+[
+    {
+        "url": "https://github.com/streamlink/streamlink-assets/releases/download/2020.4.21/ffmpeg-4.2.2-win32-static.zip",
+        "sha256": "1f6adff50db6cad54fdab15013c4c95cb6f83d7fe6d1167f3896cf4550573565",
+        "filename": "ffmpeg-4.2.2-win32-static.zip",
+        "type": "zip",
+        "sourcedir": "ffmpeg-4.2.2-win32-static",
+        "targetdir": "ffmpeg",
+        "files": [
+            {
+                "from": "bin/ffmpeg.exe",
+                "to": "ffmpeg.exe"
+            },
+            {
+                "from": "LICENSE.txt",
+                "to": "LICENSE.txt"
+            }
+        ]
+    },
+    {
+        "url": "https://github.com/streamlink/streamlink-assets/releases/download/2020.4.21/ffmpeg-4.2.2-win32-static-readme.txt",
+        "sha256": "6252abd8981ff3b61728bf58868c3dab2d4f96495907bae15ebbdad6b9bb9934",
+        "filename": "ffmpeg-4.2.2-win32-static-readme.txt",
+        "type": "file",
+        "sourcedir": null,
+        "targetdir": "ffmpeg",
+        "files": [
+            {
+                "from": "ffmpeg-4.2.2-win32-static-readme.txt",
+                "to": "BUILDINFO.txt"
+            }
+        ]
+    },
+    {
+        "url": "https://github.com/streamlink/streamlink-assets/releases/download/2020.4.21/rtmpdump-2.3-windows.zip",
+        "sha256": "6948aa372f04952d5675917c6ca2c7c0bf6b109de21a4323adc93247fff0189f",
+        "filename": "rtmpdump-2.3-windows.zip",
+        "type": "zip",
+        "sourcedir": "rtmpdump-2.3",
+        "targetdir": "rtmpdump",
+        "files": [
+            {
+                "from": "rtmpdump.exe",
+                "to": "rtmpdump.exe"
+            },
+            {
+                "from": "COPYING",
+                "to": "LICENSE.txt"
+            }
+        ]
+    }
+]
diff --git a/script/makeinstaller.sh b/script/makeinstaller.sh
index 6c8a0d07..e96334cc 100755
--- a/script/makeinstaller.sh
+++ b/script/makeinstaller.sh
@@ -34,8 +34,7 @@ STREAMLINK_VERSION=$(python setup.py --version)
 STREAMLINK_VERSION_PLAIN="${STREAMLINK_VERSION%%+*}"
 STREAMLINK_INSTALLER="${1:-"streamlink-${STREAMLINK_VERSION/\+/_}"}"
 STREAMLINK_PYTHON_VERSION=3.9.6
-STREAMLINK_ASSETS_REPO="${STREAMLINK_ASSETS_REPO:-streamlink/streamlink-assets}"
-STREAMLINK_ASSETS_RELEASE="${STREAMLINK_ASSETS_RELEASE:-latest}"
+STREAMLINK_ASSETS_FILE="${ROOT}/script/makeinstaller-assets.json"
 
 CI_BUILD_NUMBER=${GITHUB_RUN_ID:-0}
 STREAMLINK_VI_VERSION="${STREAMLINK_VERSION_PLAIN}.${CI_BUILD_NUMBER}"
@@ -273,51 +272,43 @@ cp "${ROOT}/win32/config" "${files_dir}/config"
 cp "${ROOT}/LICENSE" "${files_dir}/LICENSE.txt"
 
 
-# download binary assets like ffmpeg and rtmpdump from the streamlink assets repo
-# parse the data.json manifest, validate archives and copy specific files to their destination
-log "Fetching assets data from \"${STREAMLINK_ASSETS_REPO}\" (${STREAMLINK_ASSETS_RELEASE})"
-assets_release_data=$(curl -s --fail \
-    -H 'Accept: application/vnd.github.v3+json' \
-    -H "User-Agent: ${GITHUB_REPOSITORY:-"streamlink/streamlink"}" \
-    "https://api.github.com/repos/${STREAMLINK_ASSETS_REPO}/releases/${STREAMLINK_ASSETS_RELEASE}" \
-    || err "Could not fetch release data"
-)
-assets_release_tag=$(echo "${assets_release_data}" | jq -r ".tag_name")
-assets_data=$(curl -s --fail \
-    -H "User-Agent: ${GITHUB_REPOSITORY:-"streamlink/streamlink"}" \
-    "https://raw.githubusercontent.com/${STREAMLINK_ASSETS_REPO}/${assets_release_tag}/data.json" \
-    || err "Could not fetch manifest data"
-)
+ASSETS_DATA=$(cat "${STREAMLINK_ASSETS_FILE}")
 
-log "Retrieving assets"
-while read -r filename size url; do
-    if ! [[ -f "${cache_dir}/${filename}" ]]; then
-        log "Downloading asset: ${filename} (${size} Bytes)"
-        curl -s -L --output "${cache_dir}/${filename}" "${url}"
-    fi
-    checksum=$(jq -r "[.[] | select(.filename == \"${filename}\")] | first | .checksum" <<< "${assets_data}")
-    echo "${checksum} ${cache_dir}/${filename}" | sha256sum --check -
-done < <(jq -r '.assets[] | "\(.name) \(.size) \(.browser_download_url)"' <<< "${assets_release_data}")
+assets_prepare() {
+    log "Preparing assets"
+    while read -r filename sha256 url; do
+        if ! [[ -f "${cache_dir}/${filename}" ]]; then
+            log "Downloading asset: ${filename}"
+            curl -L -o "${cache_dir}/${filename}" "${url}"
+        fi
+        echo "${sha256} ${cache_dir}/${filename}" | sha256sum --check -
+    done < <(jq -r '.[] | "\(.filename) \(.sha256) \(.url)"' <<< "${ASSETS_DATA}")
+}
 
-log "Assembling files directory"
-TEMP=$(mktemp -d) && trap "rm -rf ${TEMP}" EXIT || exit 255
-for ((i=$(jq length <<< "${assets_data}") - 1; i >= 0; --i)); do
-    read -r filename sourcedir targetdir \
-        < <(jq -r ".[$i] | \"\(.filename) \(.sourcedir) \(.targetdir)\"" <<< "${assets_data}")
-    sourcedir="${TEMP}/${sourcedir}"
-    case "${filename}" in
-        *.zip)
-            unzip "${cache_dir}/${filename}" -d "${TEMP}"
-            ;;
-        *)
-            sourcedir="${cache_dir}"
-            ;;
-    esac
-    while read -r from to; do
-        install -v -D -T "${sourcedir}/${from}" "${files_dir}/${targetdir}/${to}"
-    done < <(jq -r ".[$i].files[] | \"\(.from) \(.to)\"" <<< "${assets_data}")
-done
+assets_assemble() {
+    log "Assembling files directory"
+    local tmp=$(mktemp -d) && trap "rm -rf '${tmp}'" RETURN || exit 255
+    for ((i=$(jq length <<< "${ASSETS_DATA}") - 1; i >= 0; --i)); do
+        read -r type filename sourcedir targetdir \
+            < <(jq -r ".[$i] | \"\(.type) \(.filename) \(.sourcedir) \(.targetdir)\"" <<< "${ASSETS_DATA}")
+        case "${type}" in
+            zip)
+                mkdir -p "${tmp}/${i}"
+                unzip "${cache_dir}/${filename}" -d "${tmp}/${i}"
+                sourcedir="${tmp}/${i}/${sourcedir}"
+                ;;
+            *)
+                sourcedir="${cache_dir}"
+                ;;
+        esac
+        while read -r from to; do
+            install -v -D -T "${sourcedir}/${from}" "${files_dir}/${targetdir}/${to}"
+        done < <(jq -r ".[$i].files[] | \"\(.from) \(.to)\"" <<< "${ASSETS_DATA}")
+    done
+}
 
+assets_prepare
+assets_assemble
 
 log "Building ${STREAMLINK_INSTALLER} installer"
 pynsist "${build_dir}/streamlink.cfg"