diff --git a/packages/mongo-livedata/oplog_observe_driver.js b/packages/mongo-livedata/oplog_observe_driver.js
index dbd44c310b..e4bbaccb73 100644
--- a/packages/mongo-livedata/oplog_observe_driver.js
+++ b/packages/mongo-livedata/oplog_observe_driver.js
@@ -55,11 +55,10 @@ OplogObserveDriver = function (options) {
       trigger, function (notification) {
         var op = notification.op;
         if (notification.dropCollection) {
-          // Defer because it may block on "wait for oplog to catch up", which
-          // isn't kosher for an oplog entry handler (will cause deadlock).
-          Meteor.defer(function () {
-            self._needToPollQuery();
-          });
+          // Note: this call is not allowed to block on anything (especially on
+          // waiting for oplog entries to catch up) because that will block
+          // onOplogEntry!
+          self._needToPollQuery();
         } else {
           // All other operators should be handled depending on phase
           if (self._phase === PHASE.QUERYING)
@@ -295,6 +294,9 @@ _.extend(OplogObserveDriver.prototype, {
   // In various circumstances, we may just want to stop processing the oplog and
   // re-run the initial query, just as if we were a PollingObserveDriver.
   //
+  // This function may not block, because it is called from an oplog entry
+  // handler.
+  //
   // XXX We should call this when we detect that we've been in FETCHING for "too
   // long".
   //
@@ -315,18 +317,27 @@ _.extend(OplogObserveDriver.prototype, {
     ++self._fetchGeneration;  // ignore any in-flight fetches
     self._phase = PHASE.QUERYING;
 
-    // subtle note: _published does not contain _id fields, but newResults does
-    var newResults = new LocalCollection._IdMap;
-    var cursor = self._cursorForQuery();
-    cursor.forEach(function (doc) {
-      newResults.set(doc._id, doc);
+    // Defer so that we don't block.
+    Meteor.defer(function () {
+      // subtle note: _published does not contain _id fields, but newResults
+      // does
+      var newResults = new LocalCollection._IdMap;
+      var cursor = self._cursorForQuery();
+      cursor.forEach(function (doc) {
+        newResults.set(doc._id, doc);
+      });
+
+      self._publishNewResults(newResults);
+
+      self._doneQuerying();
     });
-
-    self._publishNewResults(newResults);
-
-    self._doneQuerying();
   },
 
+  // Transitions to QUERYING and runs another query, or (if already in QUERYING)
+  // ensures that we will query again later.
+  //
+  // This function may not block, because it is called from an oplog entry
+  // handler.
   _needToPollQuery: function () {
     var self = this;
     if (self._stopped)