diff --git a/CMakeLists.txt b/CMakeLists.txt
index 26c86cff..35aad58a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -65,7 +65,7 @@ set(GTEST_LIBRARIES "${BINARY_DIR}/lib/${CMAKE_CFG_INTDIR}/${CMAKE_STATIC_LIBRAR
 
 ExternalProject_Add(esplugin
     PREFIX "external"
-    URL "https://github.com/Ortham/esplugin/archive/3.5.0.tar.gz"
+    URL "https://github.com/Ortham/esplugin/archive/4.0.0.tar.gz"
     CONFIGURE_COMMAND ""
     BUILD_IN_SOURCE 1
     BUILD_COMMAND cargo build --release --manifest-path ffi/Cargo.toml --target ${RUST_TARGET} &&
diff --git a/src/api/plugin.cpp b/src/api/plugin.cpp
index 9ba8bca0..f349c619 100644
--- a/src/api/plugin.cpp
+++ b/src/api/plugin.cpp
@@ -113,7 +113,7 @@ std::optional<std::string> Plugin::GetVersion() const {
 
 std::vector<std::string> Plugin::GetMasters() const {
   char** masters = nullptr;
-  uint8_t numMasters = 0;
+  size_t numMasters = 0;
   const auto ret = esp_plugin_masters(esPlugin.get(), &masters, &numMasters);
   if (ret != ESP_OK) {
     throw FileAccessError(name_ +