diff --git a/src/runtime/c/pgf/parser.cxx b/src/runtime/c/pgf/parser.cxx
index 2bdb277a3..863592957 100644
--- a/src/runtime/c/pgf/parser.cxx
+++ b/src/runtime/c/pgf/parser.cxx
@@ -51,6 +51,8 @@ struct PgfLRTableMaker::CompareItem : std::less<Item*> {
     }
 };
 
+const PgfLRTableMaker::CompareItem PgfLRTableMaker::compare_item;
+
 PgfLRTableMaker::PgfLRTableMaker(ref<PgfAbstr> abstr, ref<PgfConcr> concr)
 {
     this->abstr = abstr;
@@ -977,4 +979,4 @@ PgfExpr PgfParser::fetch(PgfDB *db, prob_t *prob)
     }
 
     return 0;
-}
\ No newline at end of file
+}