diff --git a/lix/libcmd/repl-interacter.cc b/lix/libcmd/repl-interacter.cc
index 9f11864a3..38364d49c 100644
--- a/lix/libcmd/repl-interacter.cc
+++ b/lix/libcmd/repl-interacter.cc
@@ -1,4 +1,5 @@
 #include "libutil/fmt.hh"
+#include "libutil/terminal.hh"
 #include "lix/libutil/error.hh"
 #include "lix/libutil/file-system.hh"
 #include "lix/libutil/logging.hh"
@@ -65,6 +66,9 @@ bool ReadlineLikeInteracter::getLine(std::string & input, ReplPromptType promptT
 {
     auto s = rl->ask(promptForType(promptType));
 
+    // rustyline temporarily sets a SIGWINCH handler
+    KJ_DEFER(invalidateWindowSize());
+
     return match_result(
         std::move(s),
         [&](rust::String ok) {
diff --git a/lix/libmain/shared.cc b/lix/libmain/shared.cc
index 6fdd27377..74fb300e6 100644
--- a/lix/libmain/shared.cc
+++ b/lix/libmain/shared.cc
@@ -176,12 +176,6 @@ void initNix()
     }
 
 #if __APPLE__
-    /* HACK: on darwin, we need can’t use sigprocmask with SIGWINCH.
-     * Instead, add a dummy sigaction handler, and signalHandlerThread
-     * can handle the rest. */
-    act.sa_handler = sigHandler;
-    if (sigaction(SIGWINCH, &act, 0)) throw SysError("handling SIGWINCH");
-
     /* Disable SA_RESTART for interrupts, so that system calls on this thread
      * error with EINTR like they do on Linux.
      * Most signals on BSD systems default to SA_RESTART on, but Nix
diff --git a/lix/libutil/signals.cc b/lix/libutil/signals.cc
index 0227b5f81..ad8b2f3a0 100644
--- a/lix/libutil/signals.cc
+++ b/lix/libutil/signals.cc
@@ -7,6 +7,7 @@
 #include <atomic>
 
 #include <chrono>
+#include <csignal>
 #include <map>
 #include <memory>
 #include <optional>
@@ -118,8 +119,6 @@ static void signalHandlerThread(sigset_t set)
             }
         } else if (signal == SIGTERM || signal == SIGHUP) {
             triggerInterrupt();
-        } else if (signal == SIGWINCH) {
-            updateWindowSize();
         }
     }
 }
@@ -164,7 +163,7 @@ void saveSignalMask() {
 
 void startSignalHandlerThread()
 {
-    updateWindowSize();
+    invalidateWindowSize();
     saveSignalMask();
 
     sigset_t set;
@@ -173,10 +172,11 @@ void startSignalHandlerThread()
     sigaddset(&set, SIGTERM);
     sigaddset(&set, SIGHUP);
     sigaddset(&set, SIGPIPE);
-    sigaddset(&set, SIGWINCH);
     if (pthread_sigmask(SIG_BLOCK, &set, nullptr))
         throw SysError("blocking signals");
 
+    signal(SIGWINCH, [](int) { invalidateWindowSize(); });
+
     std::thread(signalHandlerThread, set).detach();
 }
 
diff --git a/lix/libutil/terminal.cc b/lix/libutil/terminal.cc
index 162dc3a23..104bdb9c5 100644
--- a/lix/libutil/terminal.cc
+++ b/lix/libutil/terminal.cc
@@ -183,22 +183,29 @@ std::string filterANSIEscapes(std::string_view s, bool filterAll, unsigned int w
     return t;
 }
 
-static Sync<std::pair<unsigned short, unsigned short>> windowSize{{0, 0}};
+static volatile sig_atomic_t windowSizeInvalid = 0;
+static Sync<std::pair<unsigned short, unsigned short>> windowSize;
 
-void updateWindowSize()
+void invalidateWindowSize()
 {
-    struct winsize ws;
-    if (ioctl(2, TIOCGWINSZ, &ws) == 0 || ioctl(1, TIOCGWINSZ, &ws) == 0) {
-        auto windowSize_(windowSize.lock());
-        windowSize_->first = ws.ws_row;
-        windowSize_->second = ws.ws_col;
-    }
+    windowSizeInvalid = 1;
 }
 
 
 std::pair<unsigned short, unsigned short> getWindowSize()
 {
-    return *windowSize.lock();
+    auto windowSize_(windowSize.lock());
+    // this is racy, but given that window sizes change very rarely we'll just accept it
+    if (windowSizeInvalid) {
+        windowSizeInvalid = 0;
+        struct winsize ws;
+        if (ioctl(2, TIOCGWINSZ, &ws) == 0 || ioctl(1, TIOCGWINSZ, &ws) == 0) {
+            windowSize_->first = ws.ws_row;
+            windowSize_->second = ws.ws_col;
+        }
+    }
+
+    return *windowSize_;
 }
 
 std::string makeHyperlink(std::string_view linkText, std::string_view target)
diff --git a/lix/libutil/terminal.hh b/lix/libutil/terminal.hh
index 867941e5f..97178aec1 100644
--- a/lix/libutil/terminal.hh
+++ b/lix/libutil/terminal.hh
@@ -57,10 +57,10 @@ std::string filterANSIEscapes(std::string_view s,
     bool eatTabs = true);
 
 /**
- * Recalculate the window size, updating a global variable. Used in the
+ * Invalidate the window size, updating a global variable. Used in the
  * `SIGWINCH` signal handler.
  */
-void updateWindowSize();
+void invalidateWindowSize();
 
 /**
  * @return the number of rows and columns of the terminal.