diff --git a/Include/frameobject.h b/Include/frameobject.h
--- a/Include/frameobject.h
+++ b/Include/frameobject.h
@@ -42,8 +42,8 @@
     int f_lasti;                /* Last instruction if called */
     /* Call PyFrame_GetLineNumber() instead of reading this field
        directly.  As of 2.3 f_lineno is only valid when tracing is
-       active (i.e. when f_trace is set).  At other times we use
-       PyCode_Addr2Line to calculate the line from the current
+       active (i.e. when f_trace is set and not Py_None).  At other times
+       we use PyCode_Addr2Line to calculate the line from the current
        bytecode index. */
     int f_lineno;               /* Current line number */
     int f_iblock;               /* index in f_blockstack */
diff --git a/Lib/bdb.py b/Lib/bdb.py
--- a/Lib/bdb.py
+++ b/Lib/bdb.py
@@ -74,7 +74,13 @@
             self.botframe = frame.f_back # (CT) Note that this may also be None!
             return self.trace_dispatch
         if not (self.stop_here(frame) or self.break_anywhere(frame)):
-            # No need to trace this function
+            # When frame is stopframe, we are re-entering a generator frame
+            # where the {next, until, return} command had been previously
+            # issued, so we need to enable tracing in this function.
+            if (self.stopframe is frame and
+                    frame.f_code.co_flags & CO_GENERATOR):
+                return self.trace_dispatch
+            # No need to trace this function.
             return # None
         # Ignore call events in generator except when stepping.
         if self.stopframe and frame.f_code.co_flags & CO_GENERATOR:
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -30,7 +30,7 @@
 int
 PyFrame_GetLineNumber(PyFrameObject *f)
 {
-    if (f->f_trace)
+    if (f->f_trace && f->f_trace != Py_None)
         return f->f_lineno;
     else
         return PyCode_Addr2Line(f->f_code, f->f_lasti);
@@ -93,7 +93,7 @@
 
     /* You can only do this from within a trace function, not via
      * _getframe or similar hackery. */
-    if (!f->f_trace)
+    if (!f->f_trace || f->f_trace == Py_None)
     {
         PyErr_Format(PyExc_ValueError,
                      "f_lineno can only be set by a"
diff --git a/Python/ceval.c b/Python/ceval.c
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1288,7 +1288,8 @@
         /* line-by-line tracing support */
 
         if (_Py_TracingPossible &&
-            tstate->c_tracefunc != NULL && !tstate->tracing) {
+                tstate->c_tracefunc != NULL && !tstate->tracing &&
+                f->f_trace != Py_None) {
             int err;
             /* see maybe_call_line_trace
                for expository comments */
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -424,12 +424,13 @@
 {
     PyObject *callback;
     PyObject *result;
+    PyObject *temp;
 
     if (what == PyTrace_CALL)
         callback = self;
     else
         callback = frame->f_trace;
-    if (callback == NULL)
+    if (callback == NULL || callback == Py_None)
         return 0;
     result = call_trampoline(callback, frame, what, arg);
     if (result == NULL) {
@@ -438,15 +439,10 @@
         frame->f_trace = NULL;
         return -1;
     }
-    if (result != Py_None) {
-        PyObject *temp = frame->f_trace;
-        frame->f_trace = NULL;
-        Py_XDECREF(temp);
-        frame->f_trace = result;
-    }
-    else {
-        Py_DECREF(result);
-    }
+    temp = frame->f_trace;
+    frame->f_trace = NULL;
+    Py_XDECREF(temp);
+    frame->f_trace = result;
     return 0;
 }