diff --git a/src/datalink.cpp b/src/datalink.cpp
index 3e98285..f8b1322 100644
--- a/src/datalink.cpp
+++ b/src/datalink.cpp
@@ -174,7 +174,7 @@ void dl_ethernet(u_char *user, const struct pcap_pkthdr *h, const u_char *p)
         std::string s(std::string("warning: caught std::logic_error ")
                       + e.what()
                       + std::string(" in packet"));
-        DEBUG(6)(s.c_str());
+        DEBUG(6)("%s", s.c_str());
     }
 }