diff --git a/lldb/include/lldb/Interpreter/ScriptInterpreter.h b/lldb/include/lldb/Interpreter/ScriptInterpreter.h
--- a/lldb/include/lldb/Interpreter/ScriptInterpreter.h
+++ b/lldb/include/lldb/Interpreter/ScriptInterpreter.h
@@ -315,8 +315,7 @@
 
   Status SetBreakpointCommandCallbackFunction(
       std::vector<BreakpointOptions *> &bp_options_vec,
-      const char *function_name, 
-      StructuredData::ObjectSP extra_args_sp);
+      const char *function_name, StructuredData::ObjectSP extra_args_sp);
 
   /// Set a script function as the callback for the breakpoint.
   virtual Status
@@ -472,9 +471,9 @@
   const char *GetScriptInterpreterPtyName();
 
   int GetMasterFileDescriptor();
-  
-  virtual llvm::Expected<size_t> 
-  GetNumFixedArgumentsForCallable(const llvm::StringRef &callable_name) { 
+
+  virtual llvm::Expected<unsigned>
+  GetMaxPositionalArgumentsForCallable(const llvm::StringRef &callable_name) {
     return llvm::createStringError(
     llvm::inconvertibleErrorCode(), "Unimplemented function");
   }
diff --git a/lldb/scripts/Python/python-wrapper.swig b/lldb/scripts/Python/python-wrapper.swig
--- a/lldb/scripts/Python/python-wrapper.swig
+++ b/lldb/scripts/Python/python-wrapper.swig
@@ -61,20 +61,24 @@
     if (!pfunc.IsAllocated())
         return stop_at_breakpoint;
 
+    unsigned max_positional_args = PythonCallable::ArgInfo::UNBOUNDED;
+    if (auto arg_info = pfunc.GetArgInfo()) {
+        max_positional_args = arg_info.get().max_positional_args;
+    } else {
+        llvm::consumeError(arg_info.takeError());
+    }
+
     PythonObject frame_arg(PyRefType::Owned, SBTypeToSWIGWrapper(sb_frame));
     PythonObject bp_loc_arg(PyRefType::Owned, SBTypeToSWIGWrapper(sb_bp_loc));
 
     PythonObject result;
     // If the called function doesn't take extra_args, drop them here:
-    auto arg_info = pfunc.GetNumArguments();
-    if (arg_info.count == 3)
-      result = pfunc(frame_arg, bp_loc_arg, dict);
-    else if (arg_info.count == 4) {
+    if (max_positional_args < 4) {
+        result = pfunc(frame_arg, bp_loc_arg, dict);
+    } else {
         lldb::SBStructuredData *args_value = new lldb::SBStructuredData(args_impl);
         PythonObject args_arg(PyRefType::Owned, SBTypeToSWIGWrapper(args_value));
-        result = pfunc(frame_arg, bp_loc_arg, args_arg, dict);      
-    } else {
-      return stop_at_breakpoint;
+        result = pfunc(frame_arg, bp_loc_arg, args_arg, dict);
     }
 
     if (result.get() == Py_False)
diff --git a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp
--- a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp
+++ b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp
@@ -782,10 +782,9 @@
   return m_sys_module_dict;
 }
 
-llvm::Expected<size_t>
-ScriptInterpreterPythonImpl::GetNumFixedArgumentsForCallable(
-    const llvm::StringRef &callable_name)
-{
+llvm::Expected<unsigned>
+ScriptInterpreterPythonImpl::GetMaxPositionalArgumentsForCallable(
+    const llvm::StringRef &callable_name) {
   if (callable_name.empty()) {
     return llvm::createStringError(
         llvm::inconvertibleErrorCode(),
@@ -796,16 +795,15 @@
                  Locker::NoSTDIN);
   auto dict = PythonModule::MainModule()
       .ResolveName<PythonDictionary>(m_dictionary_name);
-  auto pfunc 
-     = PythonObject::ResolveNameWithDictionary<PythonCallable>(callable_name, 
-                                                               dict);
+  auto pfunc = PythonObject::ResolveNameWithDictionary<PythonCallable>(
+      callable_name, dict);
   if (!pfunc.IsAllocated()) {
     return llvm::createStringError(
         llvm::inconvertibleErrorCode(),
         "can't find callable: %s", callable_name.str().c_str());
   }
   PythonCallable::ArgInfo arg_info = pfunc.GetNumArguments();
-  return arg_info.count;
+  return arg_info.max_positional_args;
 }
 
 static std::string GenerateUniqueName(const char *base_name_wanted,
@@ -1232,22 +1230,22 @@
   // For now just cons up a oneliner that calls the provided function.
   std::string oneliner("return ");
   oneliner += function_name;
-  
-  llvm::Expected<size_t> maybe_args 
-      = GetNumFixedArgumentsForCallable(function_name);
+
+  llvm::Expected<unsigned> maybe_args =
+      GetMaxPositionalArgumentsForCallable(function_name);
   if (!maybe_args) {
-    error.SetErrorStringWithFormat("could not get num args: %s", 
+    error.SetErrorStringWithFormat(
+        "could not get num args: %s",
         llvm::toString(maybe_args.takeError()).c_str());
     return error;
   }
-  size_t num_args = *maybe_args;
-  
+  size_t max_args = *maybe_args;
+
   bool uses_extra_args = false;
-  if (num_args == 4) {
+  if (max_args >= 4) {
     uses_extra_args = true;
     oneliner += "(frame, bp_loc, extra_args, internal_dict)";
-  }
-  else if (num_args == 3) {
+  } else if (max_args >= 3) {
     if (extra_args_sp) {
       error.SetErrorString("cannot pass extra_args to a three argument callback"
                           );
@@ -1257,12 +1255,12 @@
     oneliner += "(frame, bp_loc, internal_dict)";
   } else {
     error.SetErrorStringWithFormat("expected 3 or 4 argument "
-                                   "function, %s has %zu",
-                                   function_name, num_args);
+                                   "function, %s can only take %zu",
+                                   function_name, max_args);
     return error;
   }
-  
-  SetBreakpointCommandCallback(bp_options, oneliner.c_str(), extra_args_sp, 
+
+  SetBreakpointCommandCallback(bp_options, oneliner.c_str(), extra_args_sp,
                                uses_extra_args);
   return error;
 }
@@ -1840,8 +1838,7 @@
 
 StructuredData::ObjectSP ScriptInterpreterPythonImpl::CreateScriptedThreadPlan(
     const char *class_name, StructuredDataImpl *args_data,
-    std::string &error_str, 
-    lldb::ThreadPlanSP thread_plan_sp) {
+    std::string &error_str, lldb::ThreadPlanSP thread_plan_sp) {
   if (class_name == nullptr || class_name[0] == '\0')
     return StructuredData::ObjectSP();
 
@@ -2145,7 +2142,7 @@
 
   std::string auto_generated_function_name(GenerateUniqueName(
       "lldb_autogen_python_bp_callback_func_", num_created_functions));
-  if (has_extra_args) 
+  if (has_extra_args)
     sstr.Printf("def %s (frame, bp_loc, extra_args, internal_dict):",
                 auto_generated_function_name.c_str());
   else
diff --git a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
--- a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
+++ b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
@@ -256,11 +256,10 @@
       BreakpointOptions *bp_options,
       std::unique_ptr<BreakpointOptions::CommandData> &data_up) override;
 
-  Status SetBreakpointCommandCallback(
-      BreakpointOptions *bp_options, 
-       const char *command_body_text,
-       StructuredData::ObjectSP extra_args_sp,
-       bool uses_extra_args);
+  Status SetBreakpointCommandCallback(BreakpointOptions *bp_options,
+                                      const char *command_body_text,
+                                      StructuredData::ObjectSP extra_args_sp,
+                                      bool uses_extra_args);
 
   /// Set a one-liner as the callback for the watchpoint.
   void SetWatchpointCommandCallback(WatchpointOptions *wp_options,
@@ -378,10 +377,9 @@
   python::PythonDictionary &GetSessionDictionary();
 
   python::PythonDictionary &GetSysModuleDictionary();
-  
-  llvm::Expected<size_t> 
-  GetNumFixedArgumentsForCallable(const llvm::StringRef &callable_name) 
-      override;
+
+  llvm::Expected<unsigned> GetMaxPositionalArgumentsForCallable(
+      const llvm::StringRef &callable_name) override;
 
   bool GetEmbeddedInterpreterModuleObjects();