diff --git a/devices/bc35_28_95_lwm2m/bc35_28_95_lwm2m.c b/devices/bc35_28_95_lwm2m/bc35_28_95_lwm2m.c
index 4a980b87..70f04dbc 100644
--- a/devices/bc35_28_95_lwm2m/bc35_28_95_lwm2m.c
+++ b/devices/bc35_28_95_lwm2m/bc35_28_95_lwm2m.c
@@ -158,6 +158,10 @@ static int bc35_28_95_signal_quality_check(void)
     }
 
     str = strstr(echo.buffer, "+CSQ:");
+    if (!str) 
+    {
+        return -1;
+    }
     sscanf(str, "+CSQ:%d,%d", &rssi, &ber);
     if (rssi == 99) {
         return -1;