diff --git a/changes/detect-full-queues b/changes/detect-full-queues
new file mode 100644
index 0000000000..c00e3ea8cc
--- /dev/null
+++ b/changes/detect-full-queues
@@ -0,0 +1,8 @@
+  o Major bugfixes:
+    - Newly created streams were allowed to read cells onto circuits,
+      even if the circuit's cell queue was blocked and waiting to drain.
+      This created potential unfairness, as older streams would be
+      blocked, but newer streams would gladly fill the queue completely.
+      We add code to detect this situation and prevent any stream from
+      getting more than one free cell.  Bugfix on 0.2.0.1-alpha.
+      Possible partial fix for bug 1298.
diff --git a/src/or/relay.c b/src/or/relay.c
index c123eb3973..88106e5d96 100644
--- a/src/or/relay.c
+++ b/src/or/relay.c
@@ -2100,12 +2100,16 @@ connection_or_unlink_all_active_circs(or_connection_t *orconn)
 
 /** Block (if <b>block</b> is true) or unblock (if <b>block</b> is false)
  * every edge connection that is using <b>circ</b> to write to <b>orconn</b>,
- * and start or stop reading as appropriate. */
-static void
+ * and start or stop reading as appropriate.
+ *
+ * Returns the number of streams whose status we changed.
+ */
+static int
 set_streams_blocked_on_circ(circuit_t *circ, or_connection_t *orconn,
                             int block)
 {
   edge_connection_t *edge = NULL;
+  int n = 0;
   if (circ->n_conn == orconn) {
     circ->streams_blocked_on_n_conn = block;
     if (CIRCUIT_IS_ORIGIN(circ))
@@ -2118,7 +2122,10 @@ set_streams_blocked_on_circ(circuit_t *circ, or_connection_t *orconn,
 
   for (; edge; edge = edge->next_stream) {
     connection_t *conn = TO_CONN(edge);
-    edge->edge_blocked_on_circ = block;
+    if (edge->edge_blocked_on_circ != block) {
+      ++n;
+      edge->edge_blocked_on_circ = block;
+    }
 
     if (!conn->read_event) {
       /* This connection is a placeholder for something; probably a DNS
@@ -2135,6 +2142,8 @@ set_streams_blocked_on_circ(circuit_t *circ, or_connection_t *orconn,
         connection_start_reading(conn);
     }
   }
+
+  return n;
 }
 
 /** Pull as many cells as possible (but no more than <b>max</b>) from the
@@ -2301,6 +2310,18 @@ append_cell_to_circuit_queue(circuit_t *circ, or_connection_t *orconn,
   if (!streams_blocked && queue->n >= CELL_QUEUE_HIGHWATER_SIZE)
     set_streams_blocked_on_circ(circ, orconn, 1); /* block streams */
 
+  if (streams_blocked) {
+    /* We must have missed a connection! */
+    int n = set_streams_blocked_on_circ(circ, orconn, 1);
+    if (n) {
+      log_info(LD_BUG, "Got a cell added to a cell queue when streams were "
+               "supposed to be blocked; found that %d streams weren't.", n);
+    } else {
+      log_info(LD_BUG, "Got a cell added to a cell queue when streams were "
+               "all blocked. We should figure out why.");
+    }
+  }
+
   if (queue->n == 1) {
     /* This was the first cell added to the queue.  We need to make this
      * circuit active. */