diff --git a/src/tools/guess-mpidefs b/src/tools/guess-mpidefs
index c8b6f559b4..473806b32c 100755
--- a/src/tools/guess-mpidefs
+++ b/src/tools/guess-mpidefs
@@ -71,7 +71,7 @@ function get_mpi_include ()
    fi
    outlist=""
    for word in ${inlist} ; do
-      len=`echo "${word}" | grep -o "^\-I" | wc -c`
+      len=`echo "${word}" | grep -o "^-I" 2>/dev/null | wc -c`
       if [ ${len} -ge 3 ] ; then
         outlist="${outlist} ${word}"
       fi
@@ -112,7 +112,7 @@ function get_mpi_link ()
    fi
    outlist=""
    for word in ${inlist} ; do
-      len=`echo "${word}" | grep -o "^\-L" | wc -c`
+      len=`echo "${word}" | grep -o "^-L" | wc -c`
       if [ ${len} -ge 3 ] ; then
         outlist="${outlist} ${word}"
       fi
@@ -153,7 +153,7 @@ function get_mpi_lib ()
    fi
    outlist=""
    for word in ${inlist} ; do
-      len=`echo "${word}" | grep -o "^\-l" | wc -c`
+      len=`echo "${word}" | grep -o "^-l" | wc -c`
       if [ ${len} -ge 3 ] ; then
         outlist="${outlist} ${word}"
       fi