diff --git a/README.md b/README.md
index c2c069da..e42706cb 100644
--- a/README.md
+++ b/README.md
@@ -195,6 +195,9 @@ There are some programs in folder *test' to test the TCP communication:
 
 ## Changelog
 
+### __WORK IN PROGRESS__
+* (Apollon77) Prevent crash case (Sentry IOBROKER-MODBUS-1C)  
+
 ### 3.1.7 (2020-07-23)
 * (Apollon77) Fix some Sentry crash reports (IOBROKER-MODBUS-N)
 
diff --git a/io-package.json b/io-package.json
index b8f04971..ee67e48a 100644
--- a/io-package.json
+++ b/io-package.json
@@ -274,7 +274,12 @@
             "sentry": {
                 "dsn": "https://0c7b6d766435448cbf4908f615efe683@sentry.iobroker.net/84"
             }
-        }
+        },
+        "dependencies": [
+            {
+                "js-controller": ">=2.0.0"
+            }
+        ]
     },
     "native": {
         "params": {
diff --git a/lib/master.js b/lib/master.js
index b2aa02a9..248984ec 100755
--- a/lib/master.js
+++ b/lib/master.js
@@ -218,6 +218,9 @@ function Master(options, adapter) {
             for (let b = 0; b < buffer.length; b++) {
                 buffer[b] = regs.config[(obj.native.address - regs.addressLow) * 2 + b];
             }
+            if (!modbusClient) {
+                return void callback('client disconnected');
+            }
             modbusClient.writeMultipleRegisters(regs.deviceId, obj.native.address, buffer)
                 .then(response => callback())
                 .catch(err => {
diff --git a/package.json b/package.json
index 1fd7f401..5e6beac5 100644
--- a/package.json
+++ b/package.json
@@ -39,9 +39,9 @@
     "@iobroker/adapter-core": "^2.4.0"
   },
   "devDependencies": {
-    "@alcalzone/release-script": "^1.4.1",
+    "@alcalzone/release-script": "^1.8.1",
     "gulp": "^4.0.2",
-    "mocha": "^8.0.1",
+    "mocha": "^8.1.3",
     "chai": "^4.2.0",
     "nan": "2.14.1",
     "modbus-stack": "^0.2.1"