diff --git a/abe-1.1-configure-c99.patch b/abe-1.1-configure-c99.patch
new file mode 100644
index 0000000..581e6cd
--- /dev/null
+++ b/abe-1.1-configure-c99.patch
@@ -0,0 +1,31 @@
+--- configure
++++ configure
+@@ -960,7 +960,7 @@ cat > conftest.$ac_ext << EOF
+ #line 961 "configure"
+ #include "confdefs.h"
+ 
+-main(){return(0);}
++int main(){return(0);}
+ EOF
+ if { (eval echo configure:966: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest${ac_exeext}; then
+   ac_cv_prog_cc_works=yes
+@@ -1418,8 +1418,8 @@ else
+ #define TOUPPER(c) (ISLOWER(c) ? 'A' + ((c) - 'a') : (c))
+ #define XOR(e, f) (((e) && !(f)) || (!(e) && (f)))
+ int main () { int i; for (i = 0; i < 256; i++)
+-if (XOR (islower (i), ISLOWER (i)) || toupper (i) != TOUPPER (i)) exit(2);
+-exit (0); }
++if (XOR (islower (i), ISLOWER (i)) || toupper (i) != TOUPPER (i)) return 2;
++return 0; }
+ 
+ EOF
+ if { (eval echo configure:1426: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest${ac_exeext} && (./conftest; exit) 2>/dev/null
+@@ -2031,7 +2031,7 @@ if test "$ac_x_libraries" = NO; then
+ cat > conftest.$ac_ext <<EOF
+ #line 2033 "configure"
+ #include "confdefs.h"
+-
++#include <X11/Intrinsic.h>
+ int main() {
+ ${x_direct_test_function}()
+ ; return 0; }
diff --git a/abe.spec b/abe.spec
index 671b31e..e4a9dd7 100644
--- a/abe.spec
+++ b/abe.spec
@@ -1,6 +1,6 @@
 Name:           abe
 Version:        1.1
-Release:        44%{?dist}
+Release:        45%{?dist}
 
 Summary:        Scrolling, platform-jumping, ancient pyramid exploring game
 License:        GPL+
@@ -22,6 +22,7 @@ Patch2:         %{name}-1.1-format.patch
 Patch3:         %{name}-1.1-aarch64.patch
 # Fix build failure with -Werror=format-security
 Patch4:         %{name}-1.1-format-security.patch
+Patch5:         %{name}-1.1-configure-c99.patch
 
 BuildRequires:  desktop-file-utils
 BuildRequires:  gcc-c++
@@ -44,6 +45,7 @@ vaguely in the style of similar games for the Commodore+4.
 %patch2
 %patch3
 %patch4
+%patch5
 
 # Fix the FSF's address
 sed 's/59 Temple Place, Suite 330, Boston, MA  02111-1307/51 Franklin Street, Suite 500, Boston, MA  02110-1335/' COPYING > COPYING.new
@@ -90,6 +92,9 @@ desktop-file-install --dir $RPM_BUILD_ROOT/%{_datadir}/applications/ %{name}.des
 %{_datadir}/icons/hicolor/*/apps/%{name}.png
 
 %changelog
+* Tue Dec 06 2022 Peter Fordham <peter.fordham@gmail.com> - 1.1-45
+- Port configure script to C99
+
 * Wed Jul 20 2022 Fedora Release Engineering <releng@fedoraproject.org> - 1.1-44
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_37_Mass_Rebuild