diff --git a/changes/bug20203 b/changes/bug20203
new file mode 100644
index 0000000000..b4809ffbd6
--- /dev/null
+++ b/changes/bug20203
@@ -0,0 +1,6 @@
+  o Major bugfixes (relay, OOM handler)
+    - Fix a timing-dependent assertion failure that could occur when we
+      tried to flush from a circuit after having freed its cells because
+      of an out-of-memory condition. Fixes bug 20203; bugfix on
+      0.2.8.1-alpha. Thanks to "cypherpunks" for help diagnosing this
+      one.
diff --git a/src/or/circuitlist.c b/src/or/circuitlist.c
index 716024df6a..5fb8be54b6 100644
--- a/src/or/circuitlist.c
+++ b/src/or/circuitlist.c
@@ -1836,8 +1836,14 @@ marked_circuit_free_cells(circuit_t *circ)
     return;
   }
   cell_queue_clear(&circ->n_chan_cells);
-  if (! CIRCUIT_IS_ORIGIN(circ))
-    cell_queue_clear(& TO_OR_CIRCUIT(circ)->p_chan_cells);
+  if (circ->n_mux)
+    circuitmux_clear_num_cells(circ->n_mux, circ);
+  if (! CIRCUIT_IS_ORIGIN(circ)) {
+    or_circuit_t *orcirc = TO_OR_CIRCUIT(circ);
+    cell_queue_clear(&orcirc->p_chan_cells);
+    if (orcirc->p_mux)
+      circuitmux_clear_num_cells(orcirc->p_mux, circ);
+  }
 }
 
 static size_t
diff --git a/src/or/relay.c b/src/or/relay.c
index eddad6a0cb..33191e1e89 100644
--- a/src/or/relay.c
+++ b/src/or/relay.c
@@ -2619,6 +2619,15 @@ channel_flush_from_first_active_circuit, (channel_t *chan, int max))
     }
 
     /* Circuitmux told us this was active, so it should have cells */
+    if (/*BUG(*/ queue->n == 0 /*)*/) {
+      log_warn(LD_BUG, "Found a supposedly active circuit with no cells "
+               "to send. Trying to recover.");
+      circuitmux_set_num_cells(cmux, circ, 0);
+      if (! circ->marked_for_close)
+        circuit_mark_for_close(circ, END_CIRC_REASON_INTERNAL);
+      continue;
+    }
+
     tor_assert(queue->n > 0);
 
     /*