diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 795500c5935..b040a2664ee 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -1278,3 +1278,62 @@ libpq_ngettext(const char *msgid, const char *msgid_plural, unsigned long n)
 }
 
 #endif							/* ENABLE_NLS */
+
+
+/*
+ * Append a formatted string to the given buffer, after translating it.  A
+ * newline is automatically appended; the format should not end with a
+ * newline.
+ */
+void
+libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
+{
+	int			save_errno = errno;
+	bool		done;
+	va_list		args;
+
+	Assert(fmt[strlen(fmt) - 1] != '\n');
+
+	if (PQExpBufferBroken(errorMessage))
+		return;					/* already failed */
+
+	/* Loop in case we have to retry after enlarging the buffer. */
+	do
+	{
+		errno = save_errno;
+		va_start(args, fmt);
+		done = appendPQExpBufferVA(errorMessage, libpq_gettext(fmt), args);
+		va_end(args);
+	} while (!done);
+
+	appendPQExpBufferChar(errorMessage, '\n');
+}
+
+/*
+ * Append a formatted string to the error message buffer of the given
+ * connection, after translating it.  A newline is automatically appended; the
+ * format should not end with a newline.
+ */
+void
+libpq_append_conn_error(PGconn *conn, const char *fmt, ...)
+{
+	int			save_errno = errno;
+	bool		done;
+	va_list		args;
+
+	Assert(fmt[strlen(fmt) - 1] != '\n');
+
+	if (PQExpBufferBroken(&conn->errorMessage))
+		return;					/* already failed */
+
+	/* Loop in case we have to retry after enlarging the buffer. */
+	do
+	{
+		errno = save_errno;
+		va_start(args, fmt);
+		done = appendPQExpBufferVA(&conn->errorMessage, libpq_gettext(fmt), args);
+		va_end(args);
+	} while (!done);
+
+	appendPQExpBufferChar(&conn->errorMessage, '\n');
+}
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index c75ed63a2c6..c24645b4696 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -887,6 +887,9 @@ extern char *libpq_ngettext(const char *msgid, const char *msgid_plural, unsigne
  */
 #undef _
 
+extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...) pg_attribute_printf(2, 3);
+extern void libpq_append_conn_error(PGconn *conn, const char *fmt, ...) pg_attribute_printf(2, 3);
+
 /*
  * These macros are needed to let error-handling code be portable between
  * Unix and Windows.  (ugh)
diff --git a/src/interfaces/libpq/nls.mk b/src/interfaces/libpq/nls.mk
index 9256b426c1d..4df544ecef5 100644
--- a/src/interfaces/libpq/nls.mk
+++ b/src/interfaces/libpq/nls.mk
@@ -1,5 +1,9 @@
 # src/interfaces/libpq/nls.mk
 CATALOG_NAME     = libpq
 GETTEXT_FILES    = fe-auth.c fe-auth-scram.c fe-connect.c fe-exec.c fe-gssapi-common.c fe-lobj.c fe-misc.c fe-protocol3.c fe-secure.c fe-secure-common.c fe-secure-gssapi.c fe-secure-openssl.c win32.c ../../port/thread.c
-GETTEXT_TRIGGERS = libpq_gettext pqInternalNotice:2
-GETTEXT_FLAGS    = libpq_gettext:1:pass-c-format pqInternalNotice:2:c-format
+GETTEXT_TRIGGERS = libpq_append_conn_error:2 \
+                   libpq_append_error:2 \
+                   libpq_gettext pqInternalNotice:2
+GETTEXT_FLAGS    = libpq_append_conn_error:2:c-format \
+                   libpq_append_error:2:c-format \
+                   libpq_gettext:1:pass-c-format pqInternalNotice:2:c-format
diff --git a/src/interfaces/libpq/pqexpbuffer.c b/src/interfaces/libpq/pqexpbuffer.c
index eb51e6d0884..10b32efdfeb 100644
--- a/src/interfaces/libpq/pqexpbuffer.c
+++ b/src/interfaces/libpq/pqexpbuffer.c
@@ -40,8 +40,6 @@ static const char oom_buffer[1] = "";
 /* Need a char * for unconstify() compatibility */
 static const char *oom_buffer_ptr = oom_buffer;
 
-static bool appendPQExpBufferVA(PQExpBuffer str, const char *fmt, va_list args) pg_attribute_printf(2, 0);
-
 
 /*
  * markPQExpBufferBroken
@@ -292,7 +290,7 @@ appendPQExpBuffer(PQExpBuffer str, const char *fmt,...)
  * Caution: callers must be sure to preserve their entry-time errno
  * when looping, in case the fmt contains "%m".
  */
-static bool
+bool
 appendPQExpBufferVA(PQExpBuffer str, const char *fmt, va_list args)
 {
 	size_t		avail;
diff --git a/src/interfaces/libpq/pqexpbuffer.h b/src/interfaces/libpq/pqexpbuffer.h
index efd652c80a3..f7a4e24c1b9 100644
--- a/src/interfaces/libpq/pqexpbuffer.h
+++ b/src/interfaces/libpq/pqexpbuffer.h
@@ -157,6 +157,16 @@ extern void printfPQExpBuffer(PQExpBuffer str, const char *fmt,...) pg_attribute
  */
 extern void appendPQExpBuffer(PQExpBuffer str, const char *fmt,...) pg_attribute_printf(2, 3);
 
+/*------------------------
+ * appendPQExpBufferVA
+ * Attempt to format data and append it to str.  Returns true if done
+ * (either successful or hard failure), false if need to retry.
+ *
+ * Caution: callers must be sure to preserve their entry-time errno
+ * when looping, in case the fmt contains "%m".
+ */
+extern bool appendPQExpBufferVA(PQExpBuffer str, const char *fmt, va_list args) pg_attribute_printf(2, 0);
+
 /*------------------------
  * appendPQExpBufferStr
  * Append the given string to a PQExpBuffer, allocating more space