Also fall-back on simple debugger if `--simple-prompt`

IPython/terminal/ptshell.py

@@ -26,7 +26,7 b' from prompt_toolkit.styles import PygmentsStyle, DynamicStyle'
 from pygments.styles import get_style_by_name, get_all_styles
 from pygments.token import Token
 
-from .debugger import TerminalPdb
+from .debugger import TerminalPdb, Pdb
 from .pt_inputhooks import get_inputhook_func
 from .interactiveshell import get_default_editor, TerminalMagics
 from .ptutils import IPythonPTCompleter, IPythonPTLexer
@@ -59,6 +59,14 b' class TerminalInteractiveShell(InteractiveShell):'
             """
             ).tag(config=True)
 
+    @observe('simple_prompt')
+    def _simple_prompt_changed(self, changes):
+        if changes['new'] == True:
+            self.debugger_cls = Pdb
+        else:
+            self.debugger_cls = TerminalPdb
+
+
     autoedit_syntax = Bool(False,
         help="auto editing of files with syntax errors.",
     ).tag(config=True)