diff --git a/tftp-c99.patch b/tftp-c99.patch
new file mode 100644
index 0000000..40bb4dd
--- /dev/null
+++ b/tftp-c99.patch
@@ -0,0 +1,50 @@
+The glibc headers do not declare bsd_signal by default.  Call signal
+instead, which is the same function as bsd_signal in current glibc.
+
+This fixes implicit function declarations and avoids build issues with
+future compilers.
+
+diff --git a/tftp/main.c b/tftp/main.c
+index fcf5a25ac654954b..7e399d414ca0dd2b 100644
+--- a/tftp/main.c
++++ b/tftp/main.c
+@@ -310,7 +310,7 @@ int main(int argc, char *argv[])
+         sp->s_proto = (char *)"udp";
+     }
+ 
+-    bsd_signal(SIGINT, intr);
++    signal(SIGINT, intr);
+ 
+     if (peerargc) {
+         /* Set peer */
+@@ -791,7 +791,7 @@ void intr(int sig)
+ {
+     (void)sig;                  /* Quiet unused warning */
+ 
+-    bsd_signal(SIGALRM, SIG_IGN);
++    signal(SIGALRM, SIG_IGN);
+     alarm(0);
+     siglongjmp(toplevel, -1);
+ }
+diff --git a/tftp/tftp.c b/tftp/tftp.c
+index 109848c4f9a5ad4e..d31553be5b76e305 100644
+--- a/tftp/tftp.c
++++ b/tftp/tftp.c
+@@ -85,7 +85,7 @@ void tftp_sendfile(int fd, const char *name, const char *mode)
+     is_request = 1;             /* First packet is the actual WRQ */
+     amount = 0;
+ 
+-    bsd_signal(SIGALRM, timer);
++    signal(SIGALRM, timer);
+     do {
+         if (is_request) {
+             size = makerequest(WRQ, name, dp, mode) - 4;
+@@ -191,7 +191,7 @@ void tftp_recvfile(int fd, const char *name, const char *mode)
+     firsttrip = 1;
+     amount = 0;
+ 
+-    bsd_signal(SIGALRM, timer);
++    signal(SIGALRM, timer);
+     do {
+         if (firsttrip) {
+             size = makerequest(RRQ, name, ap, mode);
diff --git a/tftp.spec b/tftp.spec
index 38ca1da..d3dc44c 100644
--- a/tftp.spec
+++ b/tftp.spec
@@ -3,7 +3,7 @@
 Summary: The client for the Trivial File Transfer Protocol (TFTP)
 Name: tftp
 Version: 5.2
-Release: 38%{?dist}
+Release: 39%{?dist}
 License: BSD
 URL: http://www.kernel.org/pub/software/network/tftp/
 Source0: http://www.kernel.org/pub/software/network/tftp/tftp-hpa/tftp-hpa-%{version}.tar.bz2
@@ -22,6 +22,7 @@ Patch9: tftp-doc.patch
 Patch10: tftp-enhanced-logging.patch
 Patch11: tftp-hpa-5.2-gcc10.patch
 Patch12: tftp-off-by-one.patch
+Patch13: tftp-c99.patch
 
 BuildRequires: autoconf
 BuildRequires: gcc
@@ -64,6 +65,7 @@ systemd socket activation, and is disabled by default.
 %patch10 -p1 -b .logging
 %patch11 -p1 -b .gcc10
 %patch12 -p1 -b .off-by-one
+%patch13 -p1
 
 %build
 autoreconf
@@ -105,6 +107,9 @@ install -p -m 644 %SOURCE2 ${RPM_BUILD_ROOT}%{_unitdir}
 %{_unitdir}/*
 
 %changelog
+* Sun Feb 05 2023 Florian Weimer <fweimer@redhat.com> - 5.2-39
+- Fix C99 compatibility issue (#2148911)
+
 * Sat Jan 21 2023 Fedora Release Engineering <releng@fedoraproject.org> - 5.2-38
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_38_Mass_Rebuild