Index: /issm/trunk-jpl/m4/issm_options.m4
===================================================================
--- /issm/trunk-jpl/m4/issm_options.m4	(revision 17630)
+++ /issm/trunk-jpl/m4/issm_options.m4	(revision 17631)
@@ -181,9 +181,13 @@
   			;;
 		   *)
-		      MEXLINK=$(mex -v 2>&1 < /dev/null | grep LDFLAGS     | sed -e "s/         LDFLAGS            = //g")
-	         MEXLIB=$( mex -v 2>&1 < /dev/null | grep CXXLIBS     | sed -e "s/         CXXLIBS            = //g")
-		      MEXEXT=$( mex -v 2>&1 < /dev/null | grep LDEXTENSION | sed -e "s/         LDEXTENSION        = //g")
+		      MEXLINK=$($MATLAB_ROOT/bin/mex -v 2>&1 < /dev/null | grep LDFLAGS     | sed -e "s/         LDFLAGS            = //g")
+	         MEXLIB=$( $MATLAB_ROOT/bin/mex -v 2>&1 < /dev/null | grep CXXLIBS     | sed -e "s/         CXXLIBS            = //g")
+		      MEXEXT=$( $MATLAB_ROOT/bin/mex -v 2>&1 < /dev/null | grep LDEXTENSION | sed -e "s/         LDEXTENSION        = //g")
   			;;
       esac
+	   if test "x$MEXEXT" = "x" ; then
+			AC_MSG_ERROR([Couldn't find mex... check your installation of matlab])
+	   fi
+
 		AC_SUBST([MATLABINCL])
 		AC_SUBST([MEX])