diff --git a/src/serena/symbol.py b/src/serena/symbol.py
index f8ba9dd2..5e80e93d 100644
--- a/src/serena/symbol.py
+++ b/src/serena/symbol.py
@@ -222,7 +222,7 @@ class LanguageServerSymbol(Symbol, ToStringMixin):
         """
         :return: string representation of the symbol kind (name attribute of the `SymbolKind` enum item)
         """
-        return SymbolKind(self.symbol_kind).name
+        return SymbolKind.from_int(self.symbol_kind).name
 
     @property
     def symbol_kind(self) -> SymbolKind:
diff --git a/src/solidlsp/ls.py b/src/solidlsp/ls.py
index 881f070d..432f11eb 100644
--- a/src/solidlsp/ls.py
+++ b/src/solidlsp/ls.py
@@ -1276,6 +1276,10 @@ class SolidLanguageServer(ABC):
                 item = cast(ls_types.UnifiedSymbolInformation, dict(original_symbol_dict))
                 absolute_path = os.path.join(self.repository_root_path, relative_file_path)
 
+                # handle non-standard symbol kind values (e.g., 255)
+                if "kind" in item and isinstance(item["kind"], int):
+                    item["kind"] = ls_types.SymbolKind.from_int(item["kind"])
+
                 # handle missing location and path entries
                 if "location" not in item:
                     uri = pathlib.Path(absolute_path).as_uri()
diff --git a/src/solidlsp/ls_types.py b/src/solidlsp/ls_types.py
index 0eafcfea..7be552ff 100644
--- a/src/solidlsp/ls_types.py
+++ b/src/solidlsp/ls_types.py
@@ -152,6 +152,7 @@ class SymbolKind(IntEnum):
 
     # TODO: This is a duplicate of SymbolKind in lsp_types.
 
+    Unknown = 0
     File = 1
     Module = 2
     Namespace = 3
@@ -179,6 +180,18 @@ class SymbolKind(IntEnum):
     Operator = 25
     TypeParameter = 26
 
+    @classmethod
+    def from_int(cls, value: int) -> "SymbolKind":
+        """Convert an integer to a SymbolKind.
+
+        Returns Unknown (0) for non-standard values instead of raising ValueError.
+        This handles language servers that may use custom/extended symbol kinds.
+        """
+        try:
+            return cls(value)
+        except ValueError:
+            return cls.Unknown
+
 
 class SymbolTag(IntEnum):
     """Symbol tags are extra annotations that tweak the rendering of a symbol.