diff --git a/libesmtp-c99.patch b/libesmtp-c99.patch
new file mode 100644
index 0000000..d677676
--- /dev/null
+++ b/libesmtp-c99.patch
@@ -0,0 +1,24 @@
+Index: libESMTP-1.1.0/smtp-api.c
+===================================================================
+--- libESMTP-1.1.0.orig/smtp-api.c
++++ libESMTP-1.1.0/smtp-api.c
+@@ -22,6 +22,7 @@
+ 
+ #include <config.h>
+ 
++#define _GNU_SOURCE
+ #include <stdarg.h>
+ #include <string.h>
+ #include <stdlib.h>
+Index: libESMTP-1.1.0/smtp-tls.c
+===================================================================
+--- libESMTP-1.1.0.orig/smtp-tls.c
++++ libESMTP-1.1.0/smtp-tls.c
+@@ -47,6 +47,7 @@
+ 
+ /* This stuff doesn't belong here */
+ /* vvvvvvvvvvv */
++#define _GNU_SOURCE
+ #include <sys/types.h>
+ #include <sys/stat.h>
+ #include <unistd.h>
diff --git a/libesmtp.changes b/libesmtp.changes
index e4541e3..b8ec541 100644
--- a/libesmtp.changes
+++ b/libesmtp.changes
@@ -1,3 +1,10 @@
+-------------------------------------------------------------------
+Wed Jul 10 14:41:09 UTC 2024 - Martin Jambor <mjambor@suse.com>
+
+- Added libesmtp-c99.patch which adds a required feature macro
+  definition so that strlcpy function is properly declared in the
+  standard header file.  [boo#1225800]
+
 -------------------------------------------------------------------
 Tue Dec 27 10:32:59 UTC 2022 - Paolo Stivanin <info@paolostivanin.com>
 
diff --git a/libesmtp.spec b/libesmtp.spec
index d2b5924..72c06bd 100644
--- a/libesmtp.spec
+++ b/libesmtp.spec
@@ -27,6 +27,8 @@ Group:          Development/Libraries/C and C++
 URL:            https://libesmtp.github.io/
 Source0:        https://github.com/libesmtp/libESMTP/archive/refs/tags/v%{version}.tar.gz#/%{name}-%{version}.tar.gz
 Patch0:         add_ntlm.patch
+#PATCH-FIX-UPSTREAM libesmtp-c99.patch boo#1225800 mjambor@suse.cz
+Patch1:         libesmtp-c99.patch
 BuildRequires:  libtool
 BuildRequires:  meson >= 0.50.0
 BuildRequires:  openssl-devel >= 1.1.0