diff --git a/src/session_impl.cpp b/src/session_impl.cpp
index afee8a582..531a1eebb 100644
--- a/src/session_impl.cpp
+++ b/src/session_impl.cpp
@@ -310,8 +310,9 @@ namespace aux {
 			, m_peer_id.begin());
 
 		// http-accepted characters:
+		// excluding ', since some buggy trackers don't support that
 		static char const printable[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-			"abcdefghijklmnopqrstuvwxyz-_.!~*'()";
+			"abcdefghijklmnopqrstuvwxyz-_.!~*()";
 
 		// the random number
 		for (unsigned char* i = m_peer_id.begin() + print.length();