diff --git a/Makefile b/Makefile
index 3dfceef..bb97fa4 100644
--- a/Makefile
+++ b/Makefile
@@ -42,6 +42,9 @@ test-upgrade: build
 install-staticcheck:
 	CGO_ENABLED=0 go install honnef.co/go/tools/cmd/staticcheck@latest
 
+install-ineffassign:
+	CGO_ENABLED=0 go install github.com/gordonklaus/ineffassign@v0.1.0
+
 check:
 	CGO_ENABLED=0 go vet -tags integration
 	CGO_ENABLED=0 go vet -tags website website/website.go
@@ -55,6 +58,7 @@ check:
 	CGO_ENABLED=0 staticcheck -tags link rfc/link.go
 	CGO_ENABLED=0 staticcheck -tags errata rfc/errata.go
 	CGO_ENABLED=0 staticcheck -tags xr rfc/xr.go
+	CGO_ENABLED=0 ineffassign ./...
 
 # needed for check-shadow
 install-shadow:
diff --git a/backup.go b/backup.go
index 29a7c2c..f5e669e 100644
--- a/backup.go
+++ b/backup.go
@@ -512,7 +512,6 @@ func backupctl(ctx context.Context, ctl *ctl) {
 			backupDB(db, jfpath)
 			bloompath := filepath.Join("accounts", acc.Name, "junkfilter.bloom")
 			backupFile(bloompath)
-			db = nil
 			err := jf.Close()
 			ctl.log.Check(err, "closing junkfilter")
 		}
diff --git a/develop.txt b/develop.txt
index 3ebd418..7227417 100644
--- a/develop.txt
+++ b/develop.txt
@@ -13,11 +13,12 @@ code paths are reachable/testable with mox localserve, but some use cases will
 require a full setup.
 
 Before committing, run at least "make fmt" and "make check" (which requires
-staticcheck, run "make install-staticcheck" once). Also run "make check-shadow"
-and fix any shadowed variables other than "err" (which are filtered out, but
-causes the command to always exit with an error code; run "make install-shadow"
-once to install the shadow command). If you've updated RFC references, run
-"make" in rfc/, it verifies the referenced files exist.
+staticcheck and ineffassign, run "make install-staticcheck install-ineffassign"
+once). Also run "make check-shadow" and fix any shadowed variables other than
+"err" (which are filtered out, but causes the command to always exit with an
+error code; run "make install-shadow" once to install the shadow command). If
+you've updated RFC references, run "make" in rfc/, it verifies the referenced
+files exist.
 
 When making changes to the public API of a package listed in
 apidiff/packages.txt, run "make genapidiff" to update the list of changes in
diff --git a/main.go b/main.go
index b3e03d6..f74dc5d 100644
--- a/main.go
+++ b/main.go
@@ -1960,11 +1960,12 @@ sharing most of its code.
 
 	resolver := dns.StrictResolver{}
 	var haveMX bool
-	var origNextHopAuthentic, expandedNextHopAuthentic bool
+	var expandedNextHopAuthentic bool
 	var expandedNextHop dns.Domain
 	var hosts []dns.IPDomain
 	if len(args) == 1 {
 		var permanent bool
+		var origNextHopAuthentic bool
 		var err error
 		haveMX, origNextHopAuthentic, expandedNextHopAuthentic, expandedNextHop, hosts, permanent, err = smtpclient.GatherDestinations(ctxbg, c.log.Logger, resolver, dns.IPDomain{Domain: origNextHop})
 		status := "temporary"
@@ -1998,7 +1999,6 @@ sharing most of its code.
 		d := xparseDomain(args[1], "destination host")
 		log.Printf("skipping domain mx/cname lookups, assuming domain is dnssec-protected")
 
-		origNextHopAuthentic = true
 		expandedNextHopAuthentic = true
 		expandedNextHop = d
 		hosts = []dns.IPDomain{{Domain: d}}
diff --git a/queue/hook_test.go b/queue/hook_test.go
index 802e40b..28459cb 100644
--- a/queue/hook_test.go
+++ b/queue/hook_test.go
@@ -656,7 +656,6 @@ func TestHookListFilterSort(t *testing.T) {
 	var lr []HookRetired
 	lastID = 0
 	last = ""
-	l = nil
 	for {
 		nl, err := HookRetiredList(ctxbg, HookRetiredFilter{Max: 1}, HookRetiredSort{LastID: lastID, Last: last})
 		tcheck(t, err, "list paginated")
diff --git a/queue/queue_test.go b/queue/queue_test.go
index a8dc3f4..23e815f 100644
--- a/queue/queue_test.go
+++ b/queue/queue_test.go
@@ -1435,7 +1435,6 @@ func TestListFilterSort(t *testing.T) {
 	var lr []MsgRetired
 	lastID = 0
 	last = ""
-	l = nil
 	for {
 		nl, err := RetiredList(ctxbg, RetiredFilter{Max: 1}, RetiredSort{LastID: lastID, Last: last})
 		tcheck(t, err, "list paginated")
diff --git a/smtpserver/server.go b/smtpserver/server.go
index 1bcb605..b451bc3 100644
--- a/smtpserver/server.go
+++ b/smtpserver/server.go
@@ -3424,18 +3424,16 @@ func (c *conn) deliver(ctx context.Context, recvHdrFor func(string) string, msgW
 							return fmt.Errorf("finding rejects mailbox: %v", err)
 						}
 
-						hasSpace := true
 						if !conf.KeepRejects && mbrej != nil {
-							var chl []store.Change
-							chl, hasSpace, err = a.d.acc.TidyRejectsMailbox(c.log, tx, mbrej)
+							chl, hasSpace, err := a.d.acc.TidyRejectsMailbox(c.log, tx, mbrej)
 							if err != nil {
 								return fmt.Errorf("tidying rejects mailbox: %v", err)
 							}
+							changes = append(changes, chl...)
 							if !hasSpace {
 								log.Info("not storing spammy mail to full rejects mailbox")
 								return nil
 							}
-							changes = append(changes, chl...)
 						}
 						if mbrej == nil {
 							nmb, chl, _, _, err := a.d.acc.MailboxCreate(tx, conf.RejectsMailbox, store.SpecialUse{})
diff --git a/store/search.go b/store/search.go
index ec4858a..969b664 100644
--- a/store/search.go
+++ b/store/search.go
@@ -187,7 +187,7 @@ func toLower(buf []byte) []byte {
 			copied = true
 			nr := make([]byte, len(r), len(r)+nsize+len(buf)-i)
 			copy(nr, r)
-			nr = r
+			r = nr
 		}
 		r = utf8.AppendRune(r, nc)
 	}