diff --git a/xmlto-c99-1.patch b/xmlto-c99-1.patch
new file mode 100644
index 0000000..8ba8416
--- /dev/null
+++ b/xmlto-c99-1.patch
@@ -0,0 +1,26 @@
+commit 1375e2df75530cd198bd16ac3de38e2b0d126276
+Author: Thomas Kuehne <thomas@kuehne.cn>
+Date:   Sat Dec 11 21:10:41 2021 +0100
+
+    fix -Wimplicit-int for ifsense
+    
+    fixes:
+    xmlif/xmlif.l:46:8: warning: type defaults to ‘int’ in declaration of ‘ifsense’ [-Wimplicit-int]
+       46 | static ifsense;                 /* sense of last `if' or unless seen */
+          |        ^~~~~~~
+    
+    Signed-off-by: Thomas Kuehne <thomas@kuehne.cn>
+
+diff --git a/xmlif/xmlif.l b/xmlif/xmlif.l
+index ac421367d47a2cd4..6e5970e147be21b1 100644
+--- a/xmlif/xmlif.l
++++ b/xmlif/xmlif.l
+@@ -43,7 +43,7 @@
+ 
+ static char **selections;	/* selection tokens */
+ static int nselections;		/* number of selections */
+-static ifsense;			/* sense of last `if' or unless seen */
++static int ifsense;		/* sense of last `if' or unless seen */
+ static char *attribute;		/* last attribute scanned */
+ 
+ struct stack_t {
diff --git a/xmlto-c99-2.patch b/xmlto-c99-2.patch
new file mode 100644
index 0000000..0bdd32f
--- /dev/null
+++ b/xmlto-c99-2.patch
@@ -0,0 +1,35 @@
+commit 8e34f087bf410bcc5fe445933d6ad9bae54f24b5
+Author: Thomas Kuehne <thomas@kuehne.cn>
+Date:   Sat Dec 11 21:54:50 2021 +0100
+
+    Fix return type of main function
+    
+    Fixes:
+    xmlif/xmlif.l:242:1: warning: return type defaults to ‘int’ [-Wimplicit-int]
+      242 | main(int argc, char *argv[])
+          | ^~~~
+    
+    Signed-off-by: Thomas Kuehne <thomas@kuehne.cn>
+
+diff --git a/xmlif/xmlif.l b/xmlif/xmlif.l
+index 6e5970e147be21b1..8bcc59216d41a3cb 100644
+--- a/xmlif/xmlif.l
++++ b/xmlif/xmlif.l
+@@ -239,7 +239,7 @@ WS		[ \t\n]*
+ 
+ int yywrap() {exit(0);};
+ 
+-main(int argc, char *argv[])
++int main(int argc, char *argv[])
+ {
+     int i;
+ 
+@@ -265,7 +265,7 @@ main(int argc, char *argv[])
+ 	    exit(1);
+ 	}
+ 
+-    yylex();
++    return yylex();
+ }
+ 
+ /*
diff --git a/xmlto.spec b/xmlto.spec
index 5bd0f1f..fce017b 100644
--- a/xmlto.spec
+++ b/xmlto.spec
@@ -1,13 +1,15 @@
 Summary: A tool for converting XML files to various formats
 Name: xmlto
 Version: 0.0.28
-Release: 18%{?dist}
+Release: 19%{?dist}
 License: GPLv2+
 #Older versions up to xmlto-0.0.20
 #URL: http://cyberelk.net/tim/xmlto/
 #Source0: http://cyberelk.net/tim/data/xmlto/stable/%{name}-%{version}.tar.bz2
 URL: https://pagure.io/xmlto/
 Source0: https://releases.pagure.org/%{name}/%{name}-%{version}.tar.bz2
+Patch0: xmlto-c99-1.patch
+Patch1: xmlto-c99-2.patch
 
 BuildRequires: make
 BuildRequires: docbook-xsl
@@ -52,7 +54,7 @@ This subpackage contains xmlto backend scripts for processing
 xhtml1 source format.
 
 %prep
-%setup -q
+%autosetup -p1
 
 %build
 %configure BASH=/bin/bash
@@ -86,6 +88,9 @@ make check
 %{_datadir}/xmlto/format/xhtml1/*
 
 %changelog
+* Thu Nov 24 2022 Florian Weimer <fweimer@redhat.com> - 0.0.28-19
+- Apply upstream patches to support building in stricer C99 mode
+
 * Sat Jul 23 2022 Fedora Release Engineering <releng@fedoraproject.org> - 0.0.28-18
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_37_Mass_Rebuild
 
@@ -453,4 +458,4 @@ make check
 - Built for Red Hat Linux.
 
 * Fri Nov 23 2001 Tim Waugh <twaugh@redhat.com>
-- Initial spec file.
\ No newline at end of file
+- Initial spec file.