diff --git a/chatmastermind/glossary.py b/chatmastermind/glossary.py
index 139666d..1a49fdc 100644
--- a/chatmastermind/glossary.py
+++ b/chatmastermind/glossary.py
@@ -7,7 +7,7 @@ import shutil
 import csv
 from pathlib import Path
 from dataclasses import dataclass, field
-from typing import Type, TypeVar
+from typing import Type, TypeVar, ClassVar
 
 GlossaryInst = TypeVar('GlossaryInst', bound='Glossary')
 
@@ -43,12 +43,17 @@ class Glossary:
     entries: dict[str, str] = field(default_factory=lambda: dict())
     file_path: Path | None = None
     ID: str | None = None
+    file_suffix: ClassVar[str] = '.glo'
 
     @classmethod
     def from_file(cls: Type[GlossaryInst], file_path: Path) -> GlossaryInst:
         """
         Create a glossary from the given file.
         """
+        if not file_path.exists():
+            raise GlossaryError(f"Glossary file '{file_path}' does not exist")
+        if file_path.suffix != cls.file_suffix:
+            raise GlossaryError(f"File type '{file_path.suffix}' is not supported")
         with open(file_path, "r") as fd:
             try:
                 data = yaml.load(fd, Loader=yaml.FullLoader)
@@ -72,6 +77,11 @@ class Glossary:
             self.file_path = file_path
         if not self.file_path:
             raise GlossaryError("Got no valid path to write glossary")
+        # check / add valid suffix
+        if not self.file_path.suffix:
+            self.file_path = self.file_path.with_suffix(self.file_suffix)
+        elif self.file_path.suffix != self.file_suffix:
+            raise GlossaryError(f"File suffix '{self.file_path.suffix}' is not supported")
         # write YAML
         with tempfile.NamedTemporaryFile(dir=self.file_path.parent, prefix=self.file_path.name, mode="w", delete=False) as temp_fd:
             temp_file_path = Path(temp_fd.name)