diff --git a/db.go b/db.go
index 5d3e26496..13e9fdb93 100644
--- a/db.go
+++ b/db.go
@@ -1251,7 +1251,7 @@ func (db *DB) freepages() []common.Pgid {
 	}
 
 	reachable := make(map[common.Pgid]*common.Page)
-	nofreed := make(map[common.Pgid]bool)
+	nofreed := make(common.PgidSet)
 	ech := make(chan error)
 	go func() {
 		for e := range ech {
diff --git a/internal/common/page.go b/internal/common/page.go
index 4453160bb..32dfb5bf3 100644
--- a/internal/common/page.go
+++ b/internal/common/page.go
@@ -389,3 +389,23 @@ func Mergepgids(dst, a, b Pgids) {
 	// Append what's left in follow.
 	_ = append(merged, follow...)
 }
+
+type PgidSet map[Pgid]struct{}
+
+func (s *PgidSet) Add(key Pgid) {
+	if *s == nil {
+		*s = make(map[Pgid]struct{})
+	}
+
+	(*s)[key] = struct{}{}
+}
+
+func (s *PgidSet) Has(key Pgid) bool {
+	if *s == nil {
+		return false
+	}
+
+	_, ok := (*s)[key]
+
+	return ok
+}
diff --git a/internal/common/page_test.go b/internal/common/page_test.go
index 376ab6a6c..fd9d9618b 100644
--- a/internal/common/page_test.go
+++ b/internal/common/page_test.go
@@ -70,3 +70,43 @@ func TestPgids_merge_quick(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestPgidSet_initialization(t *testing.T) {
+	var s PgidSet
+	if s != nil {
+		t.Fatal("Set must be nil")
+	}
+
+	s.Add(0)
+	if s == nil {
+		t.Fatal("Set must be initialized")
+	}
+}
+
+func TestPgidSet_set_has_added_values(t *testing.T) {
+	var s PgidSet
+	s.Add(100)
+	if len(s) != 1 || !s.Has(100) {
+		t.Fatal("Set must contain exactly one element")
+	}
+
+	s.Add(200)
+	if len(s) != 2 || !s.Has(200) {
+		t.Fatal("Set must contain exactly two elements")
+	}
+}
+
+func TestPgidSet_duplicates(t *testing.T) {
+	var s PgidSet
+	s.Add(5)
+	s.Add(5)
+	if len(s) != 1 {
+		t.Fatal("Set must still contain exactly one element after adding duplicate")
+	}
+
+	s.Add(15)
+	s.Add(15)
+	if len(s) != 2 {
+		t.Fatal("Set must still contain exactly two elements after adding duplicate")
+	}
+}
diff --git a/internal/freelist/shared.go b/internal/freelist/shared.go
index f30a69f10..333d5a43a 100644
--- a/internal/freelist/shared.go
+++ b/internal/freelist/shared.go
@@ -220,10 +220,10 @@ func (t *shared) Reload(p *common.Page) {
 
 func (t *shared) NoSyncReload(pgIds common.Pgids) {
 	// Build a cache of only pending pages.
-	pcache := make(map[common.Pgid]struct{})
+	pcache := make(common.PgidSet)
 	for _, txp := range t.pending {
 		for _, pendingID := range txp.ids {
-			pcache[pendingID] = struct{}{}
+			pcache.Add(pendingID)
 		}
 	}
 
@@ -231,7 +231,7 @@ func (t *shared) NoSyncReload(pgIds common.Pgids) {
 	// with any pages not in the pending lists.
 	a := []common.Pgid{}
 	for _, id := range pgIds {
-		if _, ok := pcache[id]; !ok {
+		if !pcache.Has(id) {
 			a = append(a, id)
 		}
 	}
diff --git a/tx_check.go b/tx_check.go
index 59edf3573..6fc652712 100644
--- a/tx_check.go
+++ b/tx_check.go
@@ -40,14 +40,14 @@ func (tx *Tx) check(cfg checkConfig, ch chan error) {
 	tx.db.loadFreelist()
 
 	// Check if any pages are double freed.
-	freed := make(map[common.Pgid]bool)
+	freed := make(common.PgidSet)
 	all := make([]common.Pgid, tx.db.freelist.Count())
 	tx.db.freelist.Copyall(all)
 	for _, id := range all {
-		if freed[id] {
+		if freed.Has(id) {
 			ch <- fmt.Errorf("page %d: already freed", id)
 		}
-		freed[id] = true
+		freed.Add(id)
 	}
 
 	// Track every reachable page.
@@ -68,7 +68,7 @@ func (tx *Tx) check(cfg checkConfig, ch chan error) {
 		// Ensure all pages below high water mark are either reachable or freed.
 		for i := common.Pgid(0); i < tx.meta.Pgid(); i++ {
 			_, isReachable := reachable[i]
-			if !isReachable && !freed[i] {
+			if !isReachable && !freed.Has(i) {
 				ch <- fmt.Errorf("page %d: unreachable unfreed", int(i))
 			}
 		}
@@ -83,13 +83,13 @@ func (tx *Tx) check(cfg checkConfig, ch chan error) {
 	}
 }
 
-func (tx *Tx) recursivelyCheckPage(pageId common.Pgid, reachable map[common.Pgid]*common.Page, freed map[common.Pgid]bool,
+func (tx *Tx) recursivelyCheckPage(pageId common.Pgid, reachable map[common.Pgid]*common.Page, freed common.PgidSet,
 	kvStringer KVStringer, ch chan error) {
 	tx.checkInvariantProperties(pageId, reachable, freed, kvStringer, ch)
 	tx.recursivelyCheckBucketInPage(pageId, reachable, freed, kvStringer, ch)
 }
 
-func (tx *Tx) recursivelyCheckBucketInPage(pageId common.Pgid, reachable map[common.Pgid]*common.Page, freed map[common.Pgid]bool,
+func (tx *Tx) recursivelyCheckBucketInPage(pageId common.Pgid, reachable map[common.Pgid]*common.Page, freed common.PgidSet,
 	kvStringer KVStringer, ch chan error) {
 	p := tx.page(pageId)
 
@@ -120,7 +120,7 @@ func (tx *Tx) recursivelyCheckBucketInPage(pageId common.Pgid, reachable map[com
 	}
 }
 
-func (tx *Tx) recursivelyCheckBucket(b *Bucket, reachable map[common.Pgid]*common.Page, freed map[common.Pgid]bool,
+func (tx *Tx) recursivelyCheckBucket(b *Bucket, reachable map[common.Pgid]*common.Page, freed common.PgidSet,
 	kvStringer KVStringer, ch chan error) {
 	// Ignore inline buckets.
 	if b.RootPage() == 0 {
@@ -138,7 +138,7 @@ func (tx *Tx) recursivelyCheckBucket(b *Bucket, reachable map[common.Pgid]*commo
 	})
 }
 
-func (tx *Tx) checkInvariantProperties(pageId common.Pgid, reachable map[common.Pgid]*common.Page, freed map[common.Pgid]bool,
+func (tx *Tx) checkInvariantProperties(pageId common.Pgid, reachable map[common.Pgid]*common.Page, freed common.PgidSet,
 	kvStringer KVStringer, ch chan error) {
 	tx.forEachPage(pageId, func(p *common.Page, _ int, stack []common.Pgid) {
 		verifyPageReachable(p, tx.meta.Pgid(), stack, reachable, freed, ch)
@@ -147,7 +147,7 @@ func (tx *Tx) checkInvariantProperties(pageId common.Pgid, reachable map[common.
 	tx.recursivelyCheckPageKeyOrder(pageId, kvStringer.KeyToString, ch)
 }
 
-func verifyPageReachable(p *common.Page, hwm common.Pgid, stack []common.Pgid, reachable map[common.Pgid]*common.Page, freed map[common.Pgid]bool, ch chan error) {
+func verifyPageReachable(p *common.Page, hwm common.Pgid, stack []common.Pgid, reachable map[common.Pgid]*common.Page, freed common.PgidSet, ch chan error) {
 	if p.Id() > hwm {
 		ch <- fmt.Errorf("page %d: out of bounds: %d (stack: %v)", int(p.Id()), int(hwm), stack)
 	}
@@ -162,7 +162,7 @@ func verifyPageReachable(p *common.Page, hwm common.Pgid, stack []common.Pgid, r
 	}
 
 	// We should only encounter un-freed leaf and branch pages.
-	if freed[p.Id()] {
+	if freed.Has(p.Id()) {
 		ch <- fmt.Errorf("page %d: reachable freed", int(p.Id()))
 	} else if !p.IsBranchPage() && !p.IsLeafPage() {
 		ch <- fmt.Errorf("page %d: invalid type: %s (stack: %v)", int(p.Id()), p.Typ(), stack)