diff --git a/irc/accounts.go b/irc/accounts.go
index c4c86e17..f676cba2 100644
--- a/irc/accounts.go
+++ b/irc/accounts.go
@@ -99,7 +99,7 @@ func (am *AccountManager) buildNickToAccountIndex() {
 	})
 
 	if err != nil {
-		am.server.logger.Error("internal", fmt.Sprintf("couldn't read reserved nicks: %v", err))
+		am.server.logger.Error("internal", "couldn't read reserved nicks", err.Error())
 	} else {
 		am.Lock()
 		am.nickToAccount = result
@@ -286,14 +286,14 @@ func (am *AccountManager) serializeCredentials(passphrase string, certfp string)
 		bcryptCost := int(am.server.Config().Accounts.Registration.BcryptCost)
 		creds.PassphraseHash, err = passwd.GenerateFromPassword([]byte(passphrase), bcryptCost)
 		if err != nil {
-			am.server.logger.Error("internal", fmt.Sprintf("could not hash password: %v", err))
+			am.server.logger.Error("internal", "could not hash password", err.Error())
 			return "", errAccountCreation
 		}
 	}
 
 	credText, err := json.Marshal(creds)
 	if err != nil {
-		am.server.logger.Error("internal", fmt.Sprintf("could not marshal credentials: %v", err))
+		am.server.logger.Error("internal", "could not marshal credentials", err.Error())
 		return "", errAccountCreation
 	}
 	return string(credText), nil
@@ -367,7 +367,7 @@ func (am *AccountManager) dispatchMailtoCallback(client *Client, casefoldedAccou
 	// config.TLS.InsecureSkipVerify
 	err = smtp.SendMail(addr, auth, config.Sender, []string{callbackValue}, message)
 	if err != nil {
-		am.server.logger.Error("internal", fmt.Sprintf("Failed to dispatch e-mail: %v", err))
+		am.server.logger.Error("internal", "Failed to dispatch e-mail", err.Error())
 	}
 	return
 }
@@ -619,7 +619,7 @@ func (am *AccountManager) deserializeRawAccount(raw rawClientAccount) (result Cl
 	result.RegisteredAt = time.Unix(regTimeInt, 0)
 	e := json.Unmarshal([]byte(raw.Credentials), &result.Credentials)
 	if e != nil {
-		am.server.logger.Error("internal", fmt.Sprintf("could not unmarshal credentials: %v", e))
+		am.server.logger.Error("internal", "could not unmarshal credentials", e.Error())
 		err = errAccountDoesNotExist
 		return
 	}
@@ -628,7 +628,7 @@ func (am *AccountManager) deserializeRawAccount(raw rawClientAccount) (result Cl
 	if raw.VHost != "" {
 		e := json.Unmarshal([]byte(raw.VHost), &result.VHost)
 		if e != nil {
-			am.server.logger.Warning("internal", fmt.Sprintf("could not unmarshal vhost for account %s: %v", result.Name, e))
+			am.server.logger.Warning("internal", "could not unmarshal vhost for account", result.Name, e.Error())
 			// pretend they have no vhost and move on
 		}
 	}
diff --git a/irc/channel.go b/irc/channel.go
index 7144da9b..579d3fd6 100644
--- a/irc/channel.go
+++ b/irc/channel.go
@@ -48,7 +48,7 @@ type Channel struct {
 func NewChannel(s *Server, name string, regInfo *RegisteredChannel) *Channel {
 	casefoldedName, err := CasefoldChannel(name)
 	if err != nil {
-		s.logger.Error("internal", fmt.Sprintf("Bad channel name %s: %v", name, err))
+		s.logger.Error("internal", "Bad channel name", name, err.Error())
 		return nil
 	}
 
diff --git a/irc/client_lookup_set.go b/irc/client_lookup_set.go
index 65ed3a4b..e54e29b6 100644
--- a/irc/client_lookup_set.go
+++ b/irc/client_lookup_set.go
@@ -72,7 +72,7 @@ func (clients *ClientManager) removeInternal(client *Client) (err error) {
 			delete(clients.byNick, oldcfnick)
 		} else {
 			// this shouldn't happen, but we can ignore it
-			client.server.logger.Warning("internal", fmt.Sprintf("clients for nick %s out of sync", oldcfnick))
+			client.server.logger.Warning("internal", "clients for nick out of sync", oldcfnick)
 			err = errNickMissing
 		}
 	}
diff --git a/irc/handlers.go b/irc/handlers.go
index d65d0280..6aca801f 100644
--- a/irc/handlers.go
+++ b/irc/handlers.go
@@ -367,7 +367,7 @@ func authErrorToMessage(server *Server, err error) (msg string) {
 	if err == errAccountDoesNotExist || err == errAccountUnverified || err == errAccountInvalidCredentials {
 		msg = err.Error()
 	} else {
-		server.logger.Error("internal", fmt.Sprintf("sasl authentication failure: %v", err))
+		server.logger.Error("internal", "sasl authentication failure", err.Error())
 		msg = "Unknown"
 	}
 	return
diff --git a/irc/nickserv.go b/irc/nickserv.go
index 72ca453e..37973e90 100644
--- a/irc/nickserv.go
+++ b/irc/nickserv.go
@@ -443,7 +443,7 @@ func nsPasswdHandler(server *Server, client *Client, command, params string, rb
 	if err == nil {
 		nsNotice(rb, client.t("Password changed"))
 	} else {
-		server.logger.Error("internal", fmt.Sprintf("could not upgrade user password: %v", err))
+		server.logger.Error("internal", "could not upgrade user password:", err.Error())
 		nsNotice(rb, client.t("Password could not be changed due to server error"))
 	}
 }
diff --git a/irc/server.go b/irc/server.go
index 1afee925..5970f9b6 100644
--- a/irc/server.go
+++ b/irc/server.go
@@ -836,7 +836,7 @@ func (server *Server) setupPprofListener(config *Config) {
 		}
 		go func() {
 			if err := ps.ListenAndServe(); err != nil {
-				server.logger.Error("rehash", fmt.Sprintf("pprof listener failed: %v", err))
+				server.logger.Error("rehash", "pprof listener failed", err.Error())
 			}
 		}()
 		server.pprofServer = &ps