diff --git a/include/knowrob/formulas/SimpleConjunction.h b/include/knowrob/formulas/SimpleConjunction.h
index a39064d06a..9a6c180be8 100644
--- a/include/knowrob/formulas/SimpleConjunction.h
+++ b/include/knowrob/formulas/SimpleConjunction.h
@@ -38,4 +38,8 @@ namespace knowrob {
 
 } // knowrob
 
+#if FMT_VERSION >= 90000
+template <> struct fmt::formatter<knowrob::SimpleConjunction> : fmt::ostream_formatter {};
+#endif
+
 #endif //KNOWROB_SIMPLE_CONJUNCTION_H