diff --git a/m4/ax_with_curses.m4 b/m4/ax_with_curses.m4
index 5399b85..e5ff6a5 100644
--- a/m4/ax_with_curses.m4
+++ b/m4/ax_with_curses.m4
@@ -394,7 +394,7 @@ AC_DEFUN([AX_WITH_CURSES], [
     # Test for plain Curses (or if CURSES_LIB was set by user)
 
     AS_IF([test "x$with_plaincurses" != xno && test "x$ax_cv_curses_which" = xno], [
-        AS_IF([test "x$CURSES_LIB" = x], [
+        AS_IF([test "x$CURSES_LIB" != x], [
             LIBS="$ax_saved_LIBS $CURSES_LIB"
         ], [
             LIBS="$ax_saved_LIBS -lcurses"
