diff --git a/configure.in b/configure.in
index d6277bbe..bdaa48e4 100644
--- a/configure.in
+++ b/configure.in
@@ -110,11 +110,11 @@ base_LIBS="$LIBS"
 dnl Thread related checks
 AC_CHECK_LIB(pthread, pthread_exit)
 AC_CHECK_HEADER(pthread.h)
-if test "x$ac_cv_lib_pthread_pthread_exit" = "xyes" -o "x$ac_cv_header_pthread_h" = "xyes"; then
+if test "x$ac_cv_lib_pthread_pthread_exit" = "xyes" -a "x$ac_cv_header_pthread_h" = "xyes"; then
     CXXFLAGS="$CXXFLAGS -D_REENTRANT"
     CFLAGS="$CFLAGS -D_REENTRANT"
 fi
-AM_CONDITIONAL(HAVE_THREADS, test "x$ac_cv_lib_pthread_pthread_exit" = "xyes" -o "x$ac_cv_header_pthread_h" = "xyes")
+AM_CONDITIONAL(HAVE_THREADS, test "x$ac_cv_lib_pthread_pthread_exit" = "xyes" -a "x$ac_cv_header_pthread_h" = "xyes")
 
 AC_CHECK_LIB(socket, socket)
 AC_CHECK_LIB(X11, XCreateWindow)
@@ -344,7 +344,7 @@ if test "x$ac_cv_header_zlib_h" != "xyes"; then
    echo "Building zlib"
 fi
 
-if test "x$ac_cv_lib_pthread_pthread_exit" = "xyes" -o "x$ac_cv_header_pthread_h" = "xyes"; then
+if test "x$ac_cv_lib_pthread_pthread_exit" = "xyes" -a "x$ac_cv_header_pthread_h" = "xyes"; then
    echo "Threads: pthread is supported."
 else
    echo "Threads: no threads (pthreads not found.)"