diff --git a/m4/lx_check_soplex.m4 b/m4/lx_check_soplex.m4
--- a/m4/lx_check_soplex.m4
+++ b/m4/lx_check_soplex.m4
@@ -55,9 +55,9 @@
     LIBS="$lx_save_libs"
 
     if test x"$lx_soplex_found" = x"yes"; then
-      AC_DEFINE([HAVE_SOPLEX], [1], [Define to 1 if you have SOPLEX.])
+      AC_DEFINE([LEMON_HAVE_SOPLEX], [1], [Define to 1 if you have SOPLEX.])
       lx_lp_found=yes
-      AC_DEFINE([HAVE_LP], [1], [Define to 1 if you have any LP solver.])
+      AC_DEFINE([LEMON_HAVE_LP], [1], [Define to 1 if you have any LP solver.])
       AC_MSG_RESULT([yes])
     else
       SOPLEX_CXXFLAGS=""