diff --git a/src/configure.ac b/src/configure.ac
index 6fee99c..b5f217c 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -781,6 +781,7 @@
   AC_SUBST(LUA_PRO)
   AC_SUBST(LUA_LIBS)
   AC_SUBST(LUA_CFLAGS)
+  AC_SUBST(LUA_CFLAGS_EXTRA)
 fi
 
 
@@ -1201,6 +1202,7 @@
 AC_SUBST(PERL_OBJ)
 AC_SUBST(PERL_PRO)
 AC_SUBST(PERL_CFLAGS)
+AC_SUBST(PERL_CFLAGS_EXTRA)
 AC_SUBST(PERL_LIBS)
 
 AC_MSG_CHECKING(--enable-pythoninterp argument)
@@ -1433,6 +1435,7 @@
 
 AC_SUBST(PYTHON_LIBS)
 AC_SUBST(PYTHON_CFLAGS)
+AC_SUBST(PYTHON_CFLAGS_EXTRA)
 AC_SUBST(PYTHON_SRC)
 AC_SUBST(PYTHON_OBJ)
 
@@ -1650,6 +1653,7 @@
 
 AC_SUBST(PYTHON3_LIBS)
 AC_SUBST(PYTHON3_CFLAGS)
+AC_SUBST(PYTHON3_CFLAGS_EXTRA)
 AC_SUBST(PYTHON3_SRC)
 AC_SUBST(PYTHON3_OBJ)
 
@@ -1946,6 +1950,7 @@
 AC_SUBST(TCL_OBJ)
 AC_SUBST(TCL_PRO)
 AC_SUBST(TCL_CFLAGS)
+AC_SUBST(TCL_CFLAGS_EXTRA)
 AC_SUBST(TCL_LIBS)
 
 AC_MSG_CHECKING(--enable-rubyinterp argument)
@@ -2050,6 +2055,7 @@
 AC_SUBST(RUBY_OBJ)
 AC_SUBST(RUBY_PRO)
 AC_SUBST(RUBY_CFLAGS)
+AC_SUBST(RUBY_CFLAGS_EXTRA)
 AC_SUBST(RUBY_LIBS)
 
 AC_MSG_CHECKING(--enable-cscope argument)