--- old-configure.in.orig	2018-11-14 15:14:25 UTC
+++ old-configure.in
@@ -4755,7 +4776,7 @@ ac_configure_args="$_SUBDIR_CONFIG_ARGS"
 
 # --with-system-nspr will have been converted into the relevant $NSPR_CFLAGS
 # and $NSPR_LIBS.
-ac_configure_args="`echo $ac_configure_args | sed -e 's/--with-system-nspr\S* *//'`"
+ac_configure_args="`echo $ac_configure_args | sed -e 's/--with-system-nspr[^[:space:]]* *//'`"
 
 if test "$_INTL_API" = no; then
     ac_configure_args="$ac_configure_args --without-intl-api"