diff --git a/src/plugins/e-acsl/configure.ac b/src/plugins/e-acsl/configure.ac
index e206c16e456728f2836827b1b5680e6b7e4ac609..7a408e79a48a0d1eb12c503219ecdeea6b897458 100644
--- a/src/plugins/e-acsl/configure.ac
+++ b/src/plugins/e-acsl/configure.ac
@@ -88,9 +88,7 @@ AC_OUTPUT(PLUGIN_RELATIVE_PATH(doc/doxygen/doxygen.cfg), [  ])
 # Generating Makefile #
 #######################
 
-AC_SUBST(OPTIMIZED_RTL)
 AC_SUBST(MAY_RUN_TESTS)
-AC_SUBST(OCAMLVERSION)
 
 write_plugin_config(Makefile)