diff --git a/src/include/port.h b/src/include/port.h
index 818b7c7baef..f0e28ce5c53 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -513,7 +513,12 @@ extern int	pg_check_dir(const char *dir);
 /* port/pgmkdirp.c */
 extern int	pg_mkdir_p(char *path, int omode);
 
-/* port/pqsignal.c */
+/* port/pqsignal.c (see also interfaces/libpq/legacy-pqsignal.c) */
+#ifdef FRONTEND
+#define pqsignal pqsignal_fe
+#else
+#define pqsignal pqsignal_be
+#endif
 typedef void (*pqsigfunc) (SIGNAL_ARGS);
 extern pqsigfunc pqsignal(int signo, pqsigfunc func);
 
diff --git a/src/interfaces/libpq/legacy-pqsignal.c b/src/interfaces/libpq/legacy-pqsignal.c
index 08648885623..ebd1695bf07 100644
--- a/src/interfaces/libpq/legacy-pqsignal.c
+++ b/src/interfaces/libpq/legacy-pqsignal.c
@@ -28,8 +28,16 @@
  * with the semantics it had in 9.2; in particular, this has different
  * behavior for SIGALRM than the version in src/port/pqsignal.c.
  *
- * libpq itself does not use this.
+ * libpq itself does not use this, nor does anything else in our code.
+ *
+ * src/include/port.h #define's pqsignal as pqsignal_fe or pqsignal_be,
+ * but here we want to export just plain "pqsignal".  We can't rely on
+ * port.h's extern declaration either.  (The point of those #define's
+ * is to ensure that no in-tree code accidentally calls this version.)
  */
+#undef pqsignal
+extern pqsigfunc pqsignal(int signo, pqsigfunc func);
+
 pqsigfunc
 pqsignal(int signo, pqsigfunc func)
 {
diff --git a/src/port/pqsignal.c b/src/port/pqsignal.c
index d328a27279d..1169de6b81e 100644
--- a/src/port/pqsignal.c
+++ b/src/port/pqsignal.c
@@ -123,6 +123,10 @@ wrapper_handler(SIGNAL_ARGS)
  * function instead of providing potentially-bogus return values.
  * Unfortunately, that requires modifying the pqsignal() in legacy-pqsignal.c,
  * which in turn requires an SONAME bump, which is probably not worth it.
+ *
+ * Note: the actual name of this function is either pqsignal_fe when
+ * compiled with -DFRONTEND, or pqsignal_be when compiled without that.
+ * This is to avoid a name collision with libpq's legacy-pqsignal.c.
  */
 pqsigfunc
 pqsignal(int signo, pqsigfunc func)