diff --git a/macros b/macros
index fbe3186..2770c63 100644
--- a/macros
+++ b/macros
@@ -147,7 +147,7 @@
 
 %__global_compiler_flags	-O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches %{_hardened_cflags}
 
-%__global_cflags	%{optflags}
+%__global_cflags	%{optflags} -Werror=implicit-function-declaration -Werror=implicit-int
 %__global_cxxflags	%{optflags}
 %__global_fflags	%{optflags} -I%_fmoddir
 %__global_fcflags	%{optflags} -I%_fmoddir
diff --git a/redhat-rpm-config.spec b/redhat-rpm-config.spec
index 6c220a0..2deafb3 100644
--- a/redhat-rpm-config.spec
+++ b/redhat-rpm-config.spec
@@ -140,6 +140,9 @@ install -p -m 755 -t %{buildroot}%{_rpmconfigdir} kmod.prov
 %{_rpmconfigdir}/macros.d/macros.kmp
 
 %changelog
+* Wed Nov 30 2016 Panu Matilainen <pmatilai@redhat.com> - 60-1
+- Error on implicit function declaration and -return type for C (#1393492)
+
 * Wed Nov 30 2016 Panu Matilainen <pmatilai@redhat.com> - 59-1
 - Move global compiler flags to __global_compiler_flags macro
 - Introduce separate __global_fooflags for C, C++ and Fortran