diff --git a/platformio.ini b/platformio.ini
index cefcc8f..e6e1177 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -10,6 +10,8 @@
 
 [common]
 version = "1.3.99"
+to_old_version = "1.4.0"
+
 ##
 [env:esp32dev]
 platform = espressif32
@@ -48,6 +50,7 @@ build_flags =
     #-DNDEBUG
     -mtext-section-literals
     -DVERSION=\"${common.version}\"
+    -DTOOLDVERSION=\"${common.to_old_version}\"
     -DASYNCWEBSERVER_REGEX
     #-DCORE_DEBUG_LEVEL=3
     -DCONFIG_ARDUHAL_LOG_COLORS=1
diff --git a/src/ota.cpp b/src/ota.cpp
index b222889..ed6fc52 100644
--- a/src/ota.cpp
+++ b/src/ota.cpp
@@ -14,6 +14,34 @@ static size_t updateTotalSize = 0;
 static size_t updateWritten = 0;
 static bool isSpiffsUpdate = false;
 
+/**
+ * Compares two version strings and determines if version1 is less than version2
+ * 
+ * @param version1 First version string (format: x.y.z)
+ * @param version2 Second version string (format: x.y.z)
+ * @return true if version1 is less than version2
+ */
+bool isVersionLessThan(const String& version1, const String& version2) {
+    int major1 = 0, minor1 = 0, patch1 = 0;
+    int major2 = 0, minor2 = 0, patch2 = 0;
+    
+    // Parse version1
+    sscanf(version1.c_str(), "%d.%d.%d", &major1, &minor1, &patch1);
+    
+    // Parse version2
+    sscanf(version2.c_str(), "%d.%d.%d", &major2, &minor2, &patch2);
+    
+    // Compare major version
+    if (major1 < major2) return true;
+    if (major1 > major2) return false;
+    
+    // Major versions equal, compare minor
+    if (minor1 < minor2) return true;
+    if (minor1 > minor2) return false;
+    
+    // Minor versions equal, compare patch
+    return patch1 < patch2;
+}
 
 void backupJsonConfigs() {
     // Bambu Credentials backup
@@ -111,6 +139,16 @@ void handleUpdate(AsyncWebServer &server) {
     updateHandler->setUri("/update");
     updateHandler->setMethod(HTTP_POST);
     
+    // Check if current version is less than defined TOOLVERSION before proceeding with update
+    if (isVersionLessThan(VERSION, TOOLDVERSION)) {
+        updateHandler->onRequest([](AsyncWebServerRequest *request) {
+            request->send(400, "application/json", 
+                "{\"success\":false,\"message\":\"Your current version is too old. Please perform a full upgrade.\"}");
+        });
+        server.addHandler(updateHandler);
+        return;
+    }
+
     updateHandler->onUpload([](AsyncWebServerRequest *request, String filename,
                              size_t index, uint8_t *data, size_t len, bool final) {
         if (!index) {