diff --git a/pscp.c b/pscp.c
index cd27c395..a8e276c4 100644
--- a/pscp.c
+++ b/pscp.c
@@ -129,12 +129,6 @@ static PRINTF_LIKE(2, 3) void tell_user(FILE *stream, const char *fmt, ...)
     sfree(str2);
 }
 
-void agent_schedule_callback(void (*callback)(void *, void *, int),
-                             void *callback_ctx, void *data, int len)
-{
-    unreachable("all PSCP agent requests should be synchronous");
-}
-
 /*
  * Receive a block of data from the SSH link. Block until all data
  * is available.
diff --git a/psftp.c b/psftp.c
index ac074fdc..3b4b6eb3 100644
--- a/psftp.c
+++ b/psftp.c
@@ -2430,12 +2430,6 @@ static bool verbose = false;
 
 void ldisc_echoedit_update(Ldisc *ldisc) { }
 
-void agent_schedule_callback(void (*callback)(void *, void *, int),
-                             void *callback_ctx, void *data, int len)
-{
-    unreachable("all PSFTP agent requests should be synchronous");
-}
-
 /*
  * Receive a block of data from the SSH link. Block until all data
  * is available.
diff --git a/windows/window.c b/windows/window.c
index 8fe21856..7a82b4ce 100644
--- a/windows/window.c
+++ b/windows/window.c
@@ -67,8 +67,7 @@
 
 #define WM_IGNORE_CLIP (WM_APP + 2)
 #define WM_FULLSCR_ON_MAX (WM_APP + 3)
-#define WM_AGENT_CALLBACK (WM_APP + 4)
-#define WM_GOT_CLIPDATA (WM_APP + 6)
+#define WM_GOT_CLIPDATA (WM_APP + 4)
 
 /* Needed for Chinese support and apparently not always defined. */
 #ifndef VK_PROCESSKEY
@@ -158,13 +157,6 @@ int vtmode;
 
 static struct sesslist sesslist;       /* for saved-session menu */
 
-struct agent_callback {
-    void (*callback)(void *, void *, int);
-    void *callback_ctx;
-    void *data;
-    int len;
-};
-
 #define FONT_NORMAL 0
 #define FONT_BOLD 1
 #define FONT_UNDERLINE 2
@@ -3339,13 +3331,6 @@ static LRESULT CALLBACK WndProc(HWND hwnd, UINT message,
             term_invalidate(term);
         }
         break;
-      case WM_AGENT_CALLBACK:
-        {
-            struct agent_callback *c = (struct agent_callback *)lParam;
-            c->callback(c->callback_ctx, c->data, c->len);
-            sfree(c);
-        }
-        return 0;
       case WM_GOT_CLIPDATA:
         process_clipdata((HGLOBAL)lParam, wParam);
         return 0;
@@ -5815,17 +5800,6 @@ static int win_seat_get_userpass_input(
     return ret;
 }
 
-void agent_schedule_callback(void (*callback)(void *, void *, int),
-                             void *callback_ctx, void *data, int len)
-{
-    struct agent_callback *c = snew(struct agent_callback);
-    c->callback = callback;
-    c->callback_ctx = callback_ctx;
-    c->data = data;
-    c->len = len;
-    PostMessage(hwnd, WM_AGENT_CALLBACK, 0, (LPARAM)c);
-}
-
 static bool win_seat_set_trust_status(Seat *seat, bool trusted)
 {
     term_set_trust_status(term, trusted);
diff --git a/windows/winpgnt.c b/windows/winpgnt.c
index a24cc467..962461da 100644
--- a/windows/winpgnt.c
+++ b/windows/winpgnt.c
@@ -1161,12 +1161,6 @@ void spawn_cmd(const char *cmdline, const char *args, int show)
     }
 }
 
-void agent_schedule_callback(void (*callback)(void *, void *, int),
-                             void *callback_ctx, void *data, int len)
-{
-    unreachable("all Pageant's own agent requests should be synchronous");
-}
-
 void logevent(LogContext *logctx, const char *event)
 {
     unreachable("Pageant can't create a LogContext, so this can't be called");
diff --git a/windows/winplink.c b/windows/winplink.c
index c004025d..f708a72e 100644
--- a/windows/winplink.c
+++ b/windows/winplink.c
@@ -13,15 +13,6 @@
 #include "tree234.h"
 #include "winsecur.h"
 
-#define WM_AGENT_CALLBACK (WM_APP + 4)
-
-struct agent_callback {
-    void (*callback)(void *, void *, int);
-    void *callback_ctx;
-    void *data;
-    int len;
-};
-
 void cmdline_error(const char *fmt, ...)
 {
     va_list ap;
@@ -115,17 +106,6 @@ static Seat plink_seat[1] = {{ &plink_seat_vt }};
 
 static DWORD main_thread_id;
 
-void agent_schedule_callback(void (*callback)(void *, void *, int),
-                             void *callback_ctx, void *data, int len)
-{
-    struct agent_callback *c = snew(struct agent_callback);
-    c->callback = callback;
-    c->callback_ctx = callback_ctx;
-    c->data = data;
-    c->len = len;
-    PostThreadMessage(main_thread_id, WM_AGENT_CALLBACK, 0, (LPARAM)c);
-}
-
 /*
  *  Short description of parameters.
  */
@@ -541,8 +521,7 @@ int main(int argc, char **argv)
         handles = handle_get_events(&nhandles);
         handles = sresize(handles, nhandles+1, HANDLE);
         handles[nhandles] = winselcli_event;
-        n = MsgWaitForMultipleObjects(nhandles+1, handles, false, ticks,
-                                      QS_POSTMESSAGE);
+        n = WaitForMultipleObjects(nhandles+1, handles, false, ticks);
         if ((unsigned)(n - WAIT_OBJECT_0) < (unsigned)nhandles) {
             handle_got_event(handles[n - WAIT_OBJECT_0]);
         } else if (n == WAIT_OBJECT_0 + nhandles) {
@@ -600,15 +579,6 @@ int main(int argc, char **argv)
                         }
                 }
             }
-        } else if (n == WAIT_OBJECT_0 + nhandles + 1) {
-            MSG msg;
-            while (PeekMessage(&msg, INVALID_HANDLE_VALUE,
-                               WM_AGENT_CALLBACK, WM_AGENT_CALLBACK,
-                               PM_REMOVE)) {
-                struct agent_callback *c = (struct agent_callback *)msg.lParam;
-                c->callback(c->callback_ctx, c->data, c->len);
-                sfree(c);
-            }
         }
 
         run_toplevel_callbacks();
diff --git a/windows/winstuff.h b/windows/winstuff.h
index 7183a86e..86326f7b 100644
--- a/windows/winstuff.h
+++ b/windows/winstuff.h
@@ -658,14 +658,6 @@ void handle_sink_init(handle_sink *sink, struct handle *h);
  */
 char *agent_named_pipe_name(void);
 
-/*
- * winpgntc.c needs to schedule callbacks for asynchronous agent
- * requests. This has to be done differently in GUI and console, so
- * there's an exported function used for the purpose.
- */
-void agent_schedule_callback(void (*callback)(void *, void *, int),
-                             void *callback_ctx, void *data, int len);
-
 /*
  * Exports from winser.c.
  */