diff --git a/acinclude.m4 b/acinclude.m4
index 29274ec..5400d3b 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -2449,6 +2449,8 @@ AC_DEFUN([PHP_SETUP_ICONV], [
   dnl
   dnl Check libc first if no path is provided in --with-iconv
   dnl
+  oldLIBS=$LIBS
+  LIBS=
   if test "$PHP_ICONV" = "yes"; then
     AC_CHECK_FUNC(iconv, [
       found_iconv=yes
@@ -2460,6 +2462,7 @@ AC_DEFUN([PHP_SETUP_ICONV], [
       ])
     ])
   fi
+  LIBS=$oldLIBS
 
   dnl
   dnl Check external libs for iconv funcs