diff --git a/libguile/posix.c b/libguile/posix.c
index a28cfa3a0..f371cb23e 100644
--- a/libguile/posix.c
+++ b/libguile/posix.c
@@ -121,7 +121,7 @@ extern char *ttyname();
 # include <xlocale.h>
 #endif
 
-#if HAVE_CRYPT_H
+#ifdef HAVE_CRYPT_H
 #  include <crypt.h>
 #endif
 
@@ -1755,7 +1755,7 @@ SCM_DEFINE (scm_sync, "sync", 0, 0, 0,
    multiple cpus.  So for now we don't bother with anything fancy, just
    ensure it works.  */
 
-#if HAVE_CRYPT
+#ifdef HAVE_CRYPT
 SCM_DEFINE (scm_crypt, "crypt", 2, 0, 0,
             (SCM key, SCM salt),
 	    "Encrypt @var{key} using @var{salt} as the salt value to the\n"
@@ -1841,7 +1841,7 @@ SCM_DEFINE (scm_getlogin, "getlogin", 0, 0, 0,
 #undef FUNC_NAME
 #endif /* HAVE_GETLOGIN */
 
-#if HAVE_CUSERID
+#ifdef HAVE_CUSERID
 
 # if !HAVE_DECL_CUSERID
 extern char *cuserid (char *);
diff --git a/libguile/threads.c b/libguile/threads.c
index 8249ebf90..6bc53a80e 100644
--- a/libguile/threads.c
+++ b/libguile/threads.c
@@ -630,7 +630,7 @@ scm_i_init_thread_for_guile (SCM_STACKITEM *base, SCM parent)
 
 #if SCM_USE_PTHREAD_THREADS
 
-#if HAVE_PTHREAD_ATTR_GETSTACK && HAVE_PTHREAD_GETATTR_NP
+#if defined HAVE_PTHREAD_ATTR_GETSTACK && defined HAVE_PTHREAD_GETATTR_NP
 /* This method for GNU/Linux and perhaps some other systems.
    It's not for MacOS X or Solaris 10, since pthread_getattr_np is not
    available on them.  */