diff --git a/Makefile b/Makefile
index 1ff13c133..9ee21cae4 100644
--- a/Makefile
+++ b/Makefile
@@ -42,14 +42,14 @@ lint:
 .PHONY: test
 test:
 	@echo "hashmap freelist test"
-	TEST_FREELIST_TYPE=hashmap go test -v ${TESTFLAGS} -timeout ${TESTFLAGS_TIMEOUT}
-	TEST_FREELIST_TYPE=hashmap go test -v ${TESTFLAGS} ./internal/...
-	TEST_FREELIST_TYPE=hashmap go test -v ${TESTFLAGS} ./cmd/bbolt
+	BBOLT_VERIFY=all TEST_FREELIST_TYPE=hashmap go test -v ${TESTFLAGS} -timeout ${TESTFLAGS_TIMEOUT}
+	BBOLT_VERIFY=all TEST_FREELIST_TYPE=hashmap go test -v ${TESTFLAGS} ./internal/...
+	BBOLT_VERIFY=all TEST_FREELIST_TYPE=hashmap go test -v ${TESTFLAGS} ./cmd/bbolt
 
 	@echo "array freelist test"
-	TEST_FREELIST_TYPE=array go test -v ${TESTFLAGS} -timeout ${TESTFLAGS_TIMEOUT}
-	TEST_FREELIST_TYPE=array go test -v ${TESTFLAGS} ./internal/...
-	TEST_FREELIST_TYPE=array go test -v ${TESTFLAGS} ./cmd/bbolt
+	BBOLT_VERIFY=all TEST_FREELIST_TYPE=array go test -v ${TESTFLAGS} -timeout ${TESTFLAGS_TIMEOUT}
+	BBOLT_VERIFY=all TEST_FREELIST_TYPE=array go test -v ${TESTFLAGS} ./internal/...
+	BBOLT_VERIFY=all TEST_FREELIST_TYPE=array go test -v ${TESTFLAGS} ./cmd/bbolt
 
 .PHONY: coverage
 coverage:
@@ -76,8 +76,8 @@ install-gofail:
 .PHONY: test-failpoint
 test-failpoint:
 	@echo "[failpoint] hashmap freelist test"
-	TEST_FREELIST_TYPE=hashmap go test -v ${TESTFLAGS} -timeout 30m ./tests/failpoint
+	BBOLT_VERIFY=all TEST_FREELIST_TYPE=hashmap go test -v ${TESTFLAGS} -timeout 30m ./tests/failpoint
 
 	@echo "[failpoint] array freelist test"
-	TEST_FREELIST_TYPE=array go test -v ${TESTFLAGS} -timeout 30m ./tests/failpoint
+	BBOLT_VERIFY=all TEST_FREELIST_TYPE=array go test -v ${TESTFLAGS} -timeout 30m ./tests/failpoint
 
diff --git a/freelist.go b/freelist.go
index 29ac16c72..731d75c46 100644
--- a/freelist.go
+++ b/freelist.go
@@ -30,6 +30,7 @@ type freelist struct {
 	freemaps       map[uint64]pidSet                         // key is the size of continuous pages(span), value is a set which contains the starting pgids of same size
 	forwardMap     map[common.Pgid]uint64                    // key is start pgid, value is its span size
 	backwardMap    map[common.Pgid]uint64                    // key is end pgid, value is its span size
+	freePagesCount uint64                                    // count of free pages(hashmap version)
 	allocate       func(txid common.Txid, n int) common.Pgid // the freelist allocate func
 	free_count     func() int                                // the function which gives you free page number
 	mergeSpans     func(ids common.Pgids)                    // the mergeSpan func
diff --git a/freelist_hmap.go b/freelist_hmap.go
index 57e1e950b..0d38976a1 100644
--- a/freelist_hmap.go
+++ b/freelist_hmap.go
@@ -8,7 +8,15 @@ import (
 
 // hashmapFreeCount returns count of free pages(hashmap version)
 func (f *freelist) hashmapFreeCount() int {
-	// use the forwardMap to get the total count
+	common.Verify(func() {
+		expectedFreePageCount := f.hashmapFreeCountSlow()
+		common.Assert(int(f.freePagesCount) == expectedFreePageCount,
+			"freePagesCount (%d) is out of sync with free pages map (%d)", f.freePagesCount, expectedFreePageCount)
+	})
+	return int(f.freePagesCount)
+}
+
+func (f *freelist) hashmapFreeCountSlow() int {
 	count := 0
 	for _, size := range f.forwardMap {
 		count += int(size)
@@ -142,6 +150,7 @@ func (f *freelist) addSpan(start common.Pgid, size uint64) {
 	}
 
 	f.freemaps[size][start] = struct{}{}
+	f.freePagesCount += size
 }
 
 func (f *freelist) delSpan(start common.Pgid, size uint64) {
@@ -151,6 +160,7 @@ func (f *freelist) delSpan(start common.Pgid, size uint64) {
 	if len(f.freemaps[size]) == 0 {
 		delete(f.freemaps, size)
 	}
+	f.freePagesCount -= size
 }
 
 // initial from pgids using when use hashmap version
@@ -162,6 +172,8 @@ func (f *freelist) init(pgids []common.Pgid) {
 
 	size := uint64(1)
 	start := pgids[0]
+	// reset the counter when freelist init
+	f.freePagesCount = 0
 
 	if !sort.SliceIsSorted([]common.Pgid(pgids), func(i, j int) bool { return pgids[i] < pgids[j] }) {
 		panic("pgids not sorted")
diff --git a/freelist_test.go b/freelist_test.go
index 7297055b4..5cf40bd1c 100644
--- a/freelist_test.go
+++ b/freelist_test.go
@@ -448,6 +448,7 @@ func Test_freelist_hashmapGetFreePageIDs(t *testing.T) {
 		val = rand.Int31n(1000)
 		fm[common.Pgid(i)] = uint64(val)
 		i += val
+		f.freePagesCount += uint64(val)
 	}
 
 	f.forwardMap = fm
diff --git a/internal/common/utils.go b/internal/common/utils.go
index c94e5c6bf..bdf82a7b0 100644
--- a/internal/common/utils.go
+++ b/internal/common/utils.go
@@ -7,13 +7,6 @@ import (
 	"unsafe"
 )
 
-// Assert will panic with a given formatted message if the given condition is false.
-func Assert(condition bool, msg string, v ...interface{}) {
-	if !condition {
-		panic(fmt.Sprintf("assertion failed: "+msg, v...))
-	}
-}
-
 func LoadBucket(buf []byte) *InBucket {
 	return (*InBucket)(unsafe.Pointer(&buf[0]))
 }
diff --git a/internal/common/verify.go b/internal/common/verify.go
new file mode 100644
index 000000000..eac95e263
--- /dev/null
+++ b/internal/common/verify.go
@@ -0,0 +1,67 @@
+// Copied from https://github.com/etcd-io/etcd/blob/main/client/pkg/verify/verify.go
+package common
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+const ENV_VERIFY = "BBOLT_VERIFY"
+
+type VerificationType string
+
+const (
+	ENV_VERIFY_VALUE_ALL    VerificationType = "all"
+	ENV_VERIFY_VALUE_ASSERT VerificationType = "assert"
+)
+
+func getEnvVerify() string {
+	return strings.ToLower(os.Getenv(ENV_VERIFY))
+}
+
+func IsVerificationEnabled(verification VerificationType) bool {
+	env := getEnvVerify()
+	return env == string(ENV_VERIFY_VALUE_ALL) || env == strings.ToLower(string(verification))
+}
+
+// EnableVerifications sets `ENV_VERIFY` and returns a function that
+// can be used to bring the original settings.
+func EnableVerifications(verification VerificationType) func() {
+	previousEnv := getEnvVerify()
+	os.Setenv(ENV_VERIFY, string(verification))
+	return func() {
+		os.Setenv(ENV_VERIFY, previousEnv)
+	}
+}
+
+// EnableAllVerifications enables verification and returns a function
+// that can be used to bring the original settings.
+func EnableAllVerifications() func() {
+	return EnableVerifications(ENV_VERIFY_VALUE_ALL)
+}
+
+// DisableVerifications unsets `ENV_VERIFY` and returns a function that
+// can be used to bring the original settings.
+func DisableVerifications() func() {
+	previousEnv := getEnvVerify()
+	os.Unsetenv(ENV_VERIFY)
+	return func() {
+		os.Setenv(ENV_VERIFY, previousEnv)
+	}
+}
+
+// Verify performs verification if the assertions are enabled.
+// In the default setup running in tests and skipped in the production code.
+func Verify(f func()) {
+	if IsVerificationEnabled(ENV_VERIFY_VALUE_ASSERT) {
+		f()
+	}
+}
+
+// Assert will panic with a given formatted message if the given condition is false.
+func Assert(condition bool, msg string, v ...any) {
+	if !condition {
+		panic(fmt.Sprintf("assertion failed: "+msg, v...))
+	}
+}