diff --git a/server/middleware.go b/server/middleware.go
index c9f7918..3433447 100644
--- a/server/middleware.go
+++ b/server/middleware.go
@@ -51,7 +51,7 @@ func Authenticate(store peering.Store, key *rsa.PublicKey, funcs ...OptionFunc)
 
 			serverClaims, err := assertServerToken(key, serverToken)
 			if err != nil {
-				logger.Printf("[ERROR] %s", err)
+				logger.Printf("[ERROR] %+v", err)
 				sendError(w, http.StatusUnauthorized)
 				return
 			}
@@ -64,13 +64,13 @@ func Authenticate(store peering.Store, key *rsa.PublicKey, funcs ...OptionFunc)
 				options.IgnoredClientTokenErrors...,
 			)
 			if err != nil {
-				logger.Printf("[ERROR] %s", err)
+				logger.Printf("[ERROR] %+v", err)
 				switch err {
 				case peering.ErrPeerNotFound:
 					sendError(w, http.StatusUnauthorized)
 				case ErrNotPeered:
 					if err := store.UpdateLastContact(serverClaims.PeerID, r.RemoteAddr, time.Now()); err != nil {
-						logger.Printf("[ERROR] %s", err)
+						logger.Printf("[ERROR] %+v", err)
 						sendError(w, http.StatusInternalServerError)
 						return
 					}
@@ -78,7 +78,7 @@ func Authenticate(store peering.Store, key *rsa.PublicKey, funcs ...OptionFunc)
 					return
 				case ErrPeerRejected:
 					if err := store.UpdateLastContact(serverClaims.PeerID, r.RemoteAddr, time.Now()); err != nil {
-						logger.Printf("[ERROR] %s", err)
+						logger.Printf("[ERROR] %+v", err)
 						sendError(w, http.StatusInternalServerError)
 						return
 					}
@@ -92,19 +92,19 @@ func Authenticate(store peering.Store, key *rsa.PublicKey, funcs ...OptionFunc)
 
 			match, body, err := assertBodySum(r.Body, clientClaims.BodySum)
 			if err != nil {
-				logger.Printf("[ERROR] %s", err)
+				logger.Printf("[ERROR] %+v", err)
 				sendError(w, http.StatusInternalServerError)
 				return
 			}
 
 			if !match {
-				logger.Printf("[ERROR] %s", ErrInvalidChecksum)
+				logger.Printf("[ERROR] %+v", ErrInvalidChecksum)
 				sendError(w, http.StatusBadRequest)
 				return
 			}
 
 			if err := store.UpdateLastContact(serverClaims.PeerID, r.RemoteAddr, time.Now()); err != nil {
-				logger.Printf("[ERROR] %s", err)
+				logger.Printf("[ERROR] %+v", err)
 				sendError(w, http.StatusInternalServerError)
 				return
 			}