diff --git a/src/port/pqsignal.c b/src/port/pqsignal.c
index bbd28da0805..9dadce8357d 100644
--- a/src/port/pqsignal.c
+++ b/src/port/pqsignal.c
@@ -87,6 +87,9 @@ wrapper_handler(SIGNAL_ARGS)
 {
 	int			save_errno = errno;
 
+	Assert(postgres_signal_arg > 0);
+	Assert(postgres_signal_arg < PG_NSIG);
+
 #ifndef FRONTEND
 
 	/*
@@ -139,6 +142,7 @@ pqsignal(int signo, pqsigfunc func)
 	pqsigfunc	ret;
 #endif
 
+	Assert(signo > 0);
 	Assert(signo < PG_NSIG);
 
 	if (func != SIG_IGN && func != SIG_DFL)