diff --git a/Common/GmshConfig.h.in b/Common/GmshConfig.h.in
index c83a17dc8d70396188a031046f6693272cf1cd47..4d917e3e9632b818b564e6d6add9bd88a24cd264 100644
--- a/Common/GmshConfig.h.in
+++ b/Common/GmshConfig.h.in
@@ -45,6 +45,7 @@
 #cmakedefine HAVE_ONELAB
 #cmakedefine HAVE_ONELAB_METAMODEL
 #cmakedefine HAVE_OPENGL
+#cmakedefine HAVE_OPTHOM
 #cmakedefine HAVE_OSMESA
 #cmakedefine HAVE_PARSER
 #cmakedefine HAVE_PETSC