diff --git a/libunwind.spec b/libunwind.spec
index de52445..9f2ec8a 100644
--- a/libunwind.spec
+++ b/libunwind.spec
@@ -4,7 +4,7 @@
 Summary: An unwinding library
 Name: libunwind
 Version: 1.4.0
-Release: 2%{?dist}
+Release: 3%{?dist}
 License: BSD
 URL: http://savannah.nongnu.org/projects/libunwind
 Source: http://download-mirror.savannah.gnu.org/releases/libunwind/libunwind-%{version}.tar.gz
@@ -15,6 +15,7 @@ Patch1: libunwind-arm-default-to-exidx.patch
 ExclusiveArch: %{arm} aarch64 hppa ia64 mips ppc %{power64} s390x %{ix86} x86_64
 
 BuildRequires: automake libtool autoconf texlive-latex2man
+BuildRequires: multilib-rpm-config
 
 # host != target would cause REMOTE_ONLY build even if building i386 on x86_64.
 %global _host %{_target_platform}
@@ -48,6 +49,8 @@ make %{?_smp_mflags}
 make install DESTDIR=$RPM_BUILD_ROOT
 find $RPM_BUILD_ROOT -name '*.la' -exec rm -f {} ';'
 
+%multilib_fix_c_header --file %{_includedir}/libunwind.h
+
 # /usr/include/libunwind-ptrace.h
 # [...] aren't really part of the libunwind API.  They are implemented in
 # a archive library called libunwind-ptrace.a.
@@ -85,6 +88,9 @@ echo ====================TESTSUITE DISABLED=========================
 %{_includedir}/libunwind*.h
 
 %changelog
+* Mon Aug 10 2020 Tom Callaway <spot@fedoraproject.org> - 1.4.0-3
+- fix multilib issues with libunwind.h (bz1866512)
+
 * Tue Jul 28 2020 Fedora Release Engineering <releng@fedoraproject.org> - 1.4.0-2
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_33_Mass_Rebuild