1 files changed, 5 insertions, 2 deletions
diff --git a/Lib/pdb.py b/Lib/pdb.py
index e231d3d..a391bc1 100755
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -1753,8 +1753,11 @@ class Pdb(bdb.Bdb, cmd.Cmd):
             for alias in keys:
                 self.message("%s = %s" % (alias, self.aliases[alias]))
             return
-        if args[0] in self.aliases and len(args) == 1:
-            self.message("%s = %s" % (args[0], self.aliases[args[0]]))
+        if len(args) == 1:
+            if args[0] in self.aliases:
+                self.message("%s = %s" % (args[0], self.aliases[args[0]]))
+            else:
+                self.error(f"Unknown alias '{args[0]}'")
         else:
             self.aliases[args[0]] = ' '.join(args[1:])