diff --git a/configure.ac b/configure.ac
index 39bfe5d..75fd274 100644
--- a/configure.ac
+++ b/configure.ac
@@ -8,11 +8,11 @@ LT_INIT
 # Check for libusb-1.0
 AC_SEARCH_LIBS([libusb_init], [usb-1.0], [have_libusb=yes])
 
-if test "x${have_libusb}" = xyes; then
+AS_IF([test "x${have_libusb}" = xyes], [
     AC_CHECK_HEADERS([libusb-1.0/libusb.h], [], [have_libusb=no])
-fi
+])
 
-if test "x${have_libusb}" != xyes; then
+AS_IF([test "x${have_libusb}" != xyes], [
     AC_MSG_ERROR([
     -------------------------------------------------------
      The library libusb-1.0 and header file libusb.h
@@ -20,7 +20,7 @@ if test "x${have_libusb}" != xyes; then
      Check 'config.log' for more information.
     -------------------------------------------------------
     ])
-fi
+])
 
 AC_SUBST([X52_PKG_VERSION], [0.1])
 AC_SUBST([X52_INCLUDE], ["-I \$(top_srcdir)/libx52"])