diff --git a/include/ac/signal.h b/include/ac/signal.h
index e5776f387c3d49b1785f5a9693f25af051f00e53..a18c147a1c556739d5ed68cfd589ec90edbb17e8 100644
--- a/include/ac/signal.h
+++ b/include/ac/signal.h
@@ -33,7 +33,7 @@
 #			define LDAP_SIGUSR1	SIGSYS
 #		endif
 
-#		ifdef defined( SIGUNUSED )
+#		if defined( SIGUNUSED )
 #			define LDAP_SIGUSR2	SIGUNUSED
 #		elif defined ( SIGINFO )
 #			define LDAP_SIGUSR1	SIGINFO