--- a/src/utils/smallut.h
+++ b/src/utils/smallut.h
@@ -142,6 +142,9 @@
 bool pcSubst(const string& in, string& out, map<char, string>& subs);
 /** Substitute printf-like percents and also %(key) */
 bool pcSubst(const string& in, string& out, map<string, string>& subs);
+
+/** Append system error message */
+void catstrerror(string *reason, const char *what, int _errno);
 
 /** Compute times to help with perf issues */
 class Chrono {