diff --git a/src/input_common.cpp b/src/input_common.cpp
index f473720d2..6a025d7a9 100644
--- a/src/input_common.cpp
+++ b/src/input_common.cpp
@@ -57,7 +57,7 @@ enum {
 };
 using readb_result_t = int;
 
-static readb_result_t readb(int in_fd) {
+static readb_result_t readb(int in_fd, bool queue_is_empty) {
     assert(in_fd >= 0 && "Invalid in fd");
     universal_notifier_t& notifier = universal_notifier_t::default_notifier();
     select_wrapper_t fdset;
@@ -98,7 +98,9 @@ static readb_result_t readb(int in_fd) {
         // This may come about through readability, or through a call to poll().
         if (notifier.poll() ||
             (fdset.test(notifier_fd) && notifier.notification_fd_became_readable(notifier_fd))) {
-            return readb_uvar_notified;
+            if (env_universal_barrier() && !queue_is_empty) {
+                return readb_uvar_notified;
+            }
         }
 
         // Check stdin.
@@ -167,7 +169,7 @@ char_event_t input_event_queue_t::readch() {
             return mevt.acquire();
         }
 
-        readb_result_t rr = readb(in_);
+        readb_result_t rr = readb(in_, queue_.empty());
         switch (rr) {
             case readb_eof:
                 return char_event_type_t::eof;
@@ -178,7 +180,6 @@ char_event_t input_event_queue_t::readch() {
                 break;
 
             case readb_uvar_notified:
-                env_universal_barrier();
                 break;
 
             case readb_ioport_notified:
diff --git a/tests/checks/tmux-complete.fish b/tests/checks/tmux-complete.fish
index 4dd86aed2..28cd8154b 100644
--- a/tests/checks/tmux-complete.fish
+++ b/tests/checks/tmux-complete.fish
@@ -3,9 +3,6 @@
 # Don't run this on GitHub Actions since it's flaky.
 #REQUIRES: test "$CI" != true
 
-# HACK: THIS IS DISABLED for now, since it doesn't work at the moment.
-#REQUIRES: false
-
 # Isolated tmux.
 set -g tmpdir (mktemp -d)
 set -g tmux tmux -S $tmpdir/.tmux-socket -f /dev/null