diff --git a/src/Thesaurus.cpp b/src/Thesaurus.cpp
index a7dbca0d79..086ab6239d 100644
--- a/src/Thesaurus.cpp
+++ b/src/Thesaurus.cpp
@@ -265,7 +265,7 @@ Thesaurus::Meanings Thesaurus::lookup(docstring const & t, docstring const & lan
 }
 
 #else
-#ifndef HAVE_AIKSAURUS
+#ifndef HAVE_LIBAIKSAURUS
 Thesaurus::Thesaurus()
 {
 }