diff --git a/gtm b/gtm
index d813085..69914c9 100755
--- a/gtm
+++ b/gtm
@@ -13,6 +13,12 @@ VERSION = "2025-06-07.3"
 
 # --- Data Fetching & Utility Functions (Pure) ---
 
+def is_file_tracked_by_git(filename):
+    """Check if a file is tracked by git."""
+    cmd = ['git', 'ls-files', '--error-unmatch', filename]
+    result = subprocess.run(cmd, capture_output=True, text=True)
+    return result.returncode == 0
+
 def get_commits(filename):
     cmd = ['git', 'log', '--pretty=format:%h %ad %s', '--date=format:%Y-%m-%d %H:%M', '--', filename]
     result = subprocess.run(cmd, capture_output=True, text=True)
@@ -765,5 +771,13 @@ if __name__ == "__main__":
     if not os.path.isfile(filename):
         print(f"Error: File '{filename}' does not exist")
         sys.exit(1)
+    
+    if not is_file_tracked_by_git(filename):
+        print(f"Error: File '{filename}' is not tracked by git")
+        print("Only files that are tracked in the git repository can be viewed.")
+        print("Try adding and committing the file first:")
+        print(f"  git add {filename}")
+        print(f"  git commit -m 'Add {os.path.basename(filename)}'")
+        sys.exit(1)
         
     curses.wrapper(main, filename, args.diff, args.diff_additions, args.diff_deletions, not args.no_mouse, not args.no_wrap)