diff --git a/win32/config.vc b/win32/config.vc
index a522caadfe56..ccf10ae43ab9 100644
--- a/win32/config.vc
+++ b/win32/config.vc
@@ -529,7 +529,7 @@ d_siginfo_si_pid='undef'
 d_siginfo_si_status='undef'
 d_siginfo_si_uid='undef'
 d_siginfo_si_value='undef'
-d_signbit='undef'
+d_signbit='define'
 d_sigprocmask='undef'
 d_sigsetjmp='undef'
 d_sin6_scope_id='define'