diff --git a/ghc-configure-c99.patch b/ghc-configure-c99.patch
new file mode 100644
index 0000000..03fa3e7
--- /dev/null
+++ b/ghc-configure-c99.patch
@@ -0,0 +1,68 @@
+Submitted upstream:
+
+  <https://gitlab.haskell.org/ghc/ghc/-/merge_requests/9394>
+
+From 6b218717ac85d6dc9104f470cac0b4fb594104f4 Mon Sep 17 00:00:00 2001
+From: Florian Weimer <fweimer@redhat.com>
+Date: Tue, 22 Nov 2022 15:23:50 +0100
+Subject: [PATCH] m4/fp_leading_underscore.m4: Avoid implicit exit function
+ declaration
+Content-type: text/plain
+
+And switch to a new-style function definition.
+
+Fixes build issues with compilers that do not accept implicit function
+declarations.
+
+diff -ur ghc-8.10.7.orig/aclocal.m4 ghc-8.10.7/aclocal.m4
+--- ghc-8.10.7.orig/aclocal.m4	2021-06-29 09:24:51.000000000 +0200
++++ ghc-8.10.7/aclocal.m4	2023-01-12 12:48:11.461019327 +0100
+@@ -966,17 +966,15 @@
+ struct nlist xYzzY2[] = {{"_xYzzY2", 0},{0}};
+ #endif
+ 
+-int main(argc, argv)
+-int argc;
+-char **argv;
++int main(int argc, char **argv)
+ {
+ #if defined(HAVE_NLIST_H)
+     if(nlist(argv[0], xYzzY1) == 0 && xYzzY1[0].n_value != 0)
+-        exit(1);
++        return 1;
+     if(nlist(argv[0], xYzzY2) == 0 && xYzzY2[0].n_value != 0)
+-        exit(0);
++        return 0;
+ #endif
+-    exit(1);
++    return 1;
+ }]])],[fptools_cv_leading_underscore=yes],[fptools_cv_leading_underscore=no],[fptools_cv_leading_underscore=no])
+ ;;
+ esac]);
+Only in ghc-8.10.7: aclocal.m4.orig
+diff -ur ghc-8.10.7.orig/configure ghc-8.10.7/configure
+--- ghc-8.10.7.orig/configure	2021-08-26 19:15:31.000000000 +0200
++++ ghc-8.10.7/configure	2023-01-12 12:48:23.461897380 +0100
+@@ -15709,17 +15709,15 @@
+ struct nlist xYzzY2[] = {{"_xYzzY2", 0},{0}};
+ #endif
+ 
+-int main(argc, argv)
+-int argc;
+-char **argv;
++int main(int argc, char **argv)
+ {
+ #if defined(HAVE_NLIST_H)
+     if(nlist(argv[0], xYzzY1) == 0 && xYzzY1[0].n_value != 0)
+-        exit(1);
++        return 1;
+     if(nlist(argv[0], xYzzY2) == 0 && xYzzY2[0].n_value != 0)
+-        exit(0);
++        return 0;
+ #endif
+-    exit(1);
++    return 1;
+ }
+ _ACEOF
+ if ac_fn_c_try_run "$LINENO"
+Only in ghc-8.10.7: configure.orig
diff --git a/ghc.spec b/ghc.spec
index f441227..624df70 100644
--- a/ghc.spec
+++ b/ghc.spec
@@ -57,7 +57,7 @@ Version: 8.10.7
 # - release can only be reset if *all* library versions get bumped simultaneously
 #   (sometimes after a major release)
 # - minor release numbers for a branch should be incremented monotonically
-Release: 122%{?dist}
+Release: 123%{?dist}
 Summary: Glasgow Haskell Compiler
 
 License: BSD and HaskellReport
@@ -99,6 +99,8 @@ Patch18: Disable-unboxed-arrays.patch
 Patch24: buildpath-abi-stability.patch
 Patch26: no-missing-haddock-file-warning.patch
 
+Patch27: ghc-configure-c99.patch
+
 # fedora ghc has been bootstrapped on
 # %%{ix86} x86_64 ppc ppc64 armv7hl s390 s390x ppc64le aarch64
 # and retired arches: alpha sparcv9 armv5tel
@@ -363,6 +365,8 @@ rm -r libffi-tarballs
 %patch24 -p1 -b .orig
 %patch26 -p1 -b .orig
 
+%patch27 -p1
+
 %if %{with haddock}
 %global gen_contents_index gen_contents_index.orig
 if [ ! -f "libraries/%{gen_contents_index}" ]; then
@@ -686,6 +690,9 @@ env -C %{ghc_html_libraries_dir} ./gen_contents_index
 
 
 %changelog
+* Thu Jan 12 2023 Florian Weimer <fweimer@redhat.com> - 8.10.7-123
+- Port configure script to C99
+
 * Fri Jan  6 2023 Jens Petersen <petersen@redhat.com> - 8.10.7-122
 - obsoletes ghc8.10
 - use llvm 12 (for ARM)