diff --git a/server/device.py b/server/device.py
index 7851639a..ab08843c 100755
--- a/server/device.py
+++ b/server/device.py
@@ -637,8 +637,8 @@ icons = {
 def guess_icon(vendor, mac, ip, name,  default):
     result = default
     mac    = mac.upper()
-    vendor = vendor.lower()
-    name   = name.lower()
+    vendor = vendor.lower() if vendor else "unknown"
+    name   = name.lower() if name else "(unknown)"
 
     # Guess icon based on vendor
     if any(brand in vendor for brand in {"samsung", "motorola"}):
@@ -693,8 +693,8 @@ def guess_icon(vendor, mac, ip, name,  default):
 def guess_type(vendor, mac, ip, name,  default):
     result = default
     mac    = mac.upper()
-    vendor = vendor.lower()
-    name   = name.lower()
+    vendor = vendor.lower() if vendor else "unknown"
+    name   = name.lower() if name else "(unknown)"
 
     # Guess icon based on vendor
     if any(brand in vendor for brand in {"samsung", "motorola"}):