diff --git a/exec.c b/exec.c
index 6b92198e62..d8b2180170 100644
--- a/exec.c
+++ b/exec.c
@@ -1603,8 +1603,10 @@ void cpu_set_log(int log_flags)
             static char logfile_buf[4096];
             setvbuf(logfile, logfile_buf, _IOLBF, sizeof(logfile_buf));
         }
-#elif !defined(_WIN32)
-        /* Win32 doesn't support line-buffering and requires size >= 2 */
+#elif defined(_WIN32)
+        /* Win32 doesn't support line-buffering, so use unbuffered output. */
+        setvbuf(logfile, NULL, _IONBF, 0);
+#else
         setvbuf(logfile, NULL, _IOLBF, 0);
 #endif
         log_append = 1;