diff --git a/conn.go b/conn.go
index 18fcb61..b90ed51 100644
--- a/conn.go
+++ b/conn.go
@@ -68,6 +68,8 @@ func OpenFlags(filename string, flags OpenFlag) (conn *Conn, err error) {
 // open blob handles, and/or unfinished backup objects,
 // Close will leave the database connection open and return [BUSY].
 //
+// It is safe to close a nil, zero or closed connection.
+//
 // https://www.sqlite.org/c3ref/close.html
 func (c *Conn) Close() error {
 	if c == nil || c.handle == 0 {
@@ -179,6 +181,10 @@ func (c *Conn) Prepare(sql string) (stmt *Stmt, tail string, err error) {
 //
 // https://www.sqlite.org/c3ref/prepare.html
 func (c *Conn) PrepareFlags(sql string, flags PrepareFlag) (stmt *Stmt, tail string, err error) {
+	if emptyStatement(sql) {
+		return nil, "", nil
+	}
+
 	defer c.arena.reset()
 	stmtPtr := c.arena.new(ptrlen)
 	tailPtr := c.arena.new(ptrlen)
diff --git a/driver/driver.go b/driver/driver.go
index 4a17839..8f04b8a 100644
--- a/driver/driver.go
+++ b/driver/driver.go
@@ -99,12 +99,14 @@ func (c conn) Prepare(query string) (driver.Stmt, error) {
 	}
 	if tail != "" {
 		// Check if the tail contains any SQL.
-		s, _, err := c.conn.Prepare(tail)
+		st, _, err := c.conn.Prepare(tail)
 		if err != nil {
+			s.Close()
 			return nil, err
 		}
-		if s != nil {
+		if st != nil {
 			s.Close()
+			st.Close()
 			return nil, tailErr
 		}
 	}
diff --git a/driver/time.go b/driver/time.go
index c8f592e..0a9a5b9 100644
--- a/driver/time.go
+++ b/driver/time.go
@@ -9,8 +9,22 @@ import (
 // if it roundtrips back to the same string.
 // This way times can be persisted to, and recovered from, the database,
 // but if a string is needed, [database.sql] will recover the same string.
-// TODO: optimize and fuzz test.
 func maybeDate(text string) driver.Value {
+	// Weed out (some) values that can't possibly be
+	// [time.RFC3339Nano] timestamps.
+	if len(text) < len("2006-01-02T15:04:05") {
+		return text
+	}
+	if text[4] != '-' || text[10] != 'T' || text[16] != ':' {
+		return text
+	}
+	for _, c := range []byte(text[:4]) {
+		if c < '0' || '9' < c {
+			return text
+		}
+	}
+
+	// Slow path.
 	date, err := time.Parse(time.RFC3339Nano, text)
 	if err == nil && date.Format(time.RFC3339Nano) == text {
 		return date
diff --git a/driver/time_test.go b/driver/time_test.go
new file mode 100644
index 0000000..7fd3711
--- /dev/null
+++ b/driver/time_test.go
@@ -0,0 +1,42 @@
+package driver
+
+import (
+	"testing"
+	"time"
+)
+
+func Fuzz_maybeDate(f *testing.F) {
+	f.Add("")
+	f.Add(" ")
+	f.Add("SQLite")
+	f.Add(time.RFC3339)
+	f.Add(time.RFC3339Nano)
+	f.Add(time.Layout)
+	f.Add(time.DateTime)
+	f.Add(time.DateOnly)
+	f.Add(time.TimeOnly)
+
+	f.Fuzz(func(t *testing.T, str string) {
+		value := maybeDate(str)
+
+		switch v := value.(type) {
+		case time.Time:
+			// Make sure times round-trip to the same string:
+			// https://pkg.go.dev/database/sql#Rows.Scan
+			if v.Format(time.RFC3339Nano) != str {
+				t.Fatalf("did not round-trip: %q", str)
+			}
+		case string:
+			if v != str {
+				t.Fatalf("did not round-trip: %q", str)
+			}
+
+			date, err := time.Parse(time.RFC3339Nano, str)
+			if err == nil && date.Format(time.RFC3339Nano) == str {
+				t.Fatalf("would round-trip: %q", str)
+			}
+		default:
+			t.Fatalf("invalid type %T: %q", v, str)
+		}
+	})
+}
diff --git a/mock_test.go b/mock_test.go
new file mode 100644
index 0000000..fcb5ccc
--- /dev/null
+++ b/mock_test.go
@@ -0,0 +1,161 @@
+package sqlite3
+
+import (
+	"context"
+	"encoding/binary"
+	"math"
+
+	"github.com/tetratelabs/wazero/api"
+)
+
+func init() {
+	Path = "./embed/sqlite3.wasm"
+}
+
+func newMemory(size uint32) memory {
+	mem := make(mockMemory, size)
+	return memory{mockModule{&mem}}
+}
+
+type mockModule struct {
+	memory api.Memory
+}
+
+func (m mockModule) Memory() api.Memory { return m.memory }
+func (m mockModule) String() string     { return "mockModule" }
+func (m mockModule) Name() string       { return "mockModule" }
+
+func (m mockModule) ExportedGlobal(name string) api.Global                          { return nil }
+func (m mockModule) ExportedMemory(name string) api.Memory                          { return nil }
+func (m mockModule) ExportedFunction(name string) api.Function                      { return nil }
+func (m mockModule) ExportedMemoryDefinitions() map[string]api.MemoryDefinition     { return nil }
+func (m mockModule) ExportedFunctionDefinitions() map[string]api.FunctionDefinition { return nil }
+func (m mockModule) CloseWithExitCode(ctx context.Context, exitCode uint32) error   { return nil }
+func (m mockModule) Close(context.Context) error                                    { return nil }
+
+type mockMemory []byte
+
+func (m mockMemory) Definition() api.MemoryDefinition { return nil }
+
+func (m mockMemory) Size() uint32 { return uint32(len(m)) }
+
+func (m mockMemory) ReadByte(offset uint32) (byte, bool) {
+	if offset >= m.Size() {
+		return 0, false
+	}
+	return m[offset], true
+}
+
+func (m mockMemory) ReadUint16Le(offset uint32) (uint16, bool) {
+	if !m.hasSize(offset, 2) {
+		return 0, false
+	}
+	return binary.LittleEndian.Uint16(m[offset : offset+2]), true
+}
+
+func (m mockMemory) ReadUint32Le(offset uint32) (uint32, bool) {
+	if !m.hasSize(offset, 4) {
+		return 0, false
+	}
+	return binary.LittleEndian.Uint32(m[offset : offset+4]), true
+}
+
+func (m mockMemory) ReadFloat32Le(offset uint32) (float32, bool) {
+	v, ok := m.ReadUint32Le(offset)
+	if !ok {
+		return 0, false
+	}
+	return math.Float32frombits(v), true
+}
+
+func (m mockMemory) ReadUint64Le(offset uint32) (uint64, bool) {
+	if !m.hasSize(offset, 8) {
+		return 0, false
+	}
+	return binary.LittleEndian.Uint64(m[offset : offset+8]), true
+}
+
+func (m mockMemory) ReadFloat64Le(offset uint32) (float64, bool) {
+	v, ok := m.ReadUint64Le(offset)
+	if !ok {
+		return 0, false
+	}
+	return math.Float64frombits(v), true
+}
+
+func (m mockMemory) Read(offset, byteCount uint32) ([]byte, bool) {
+	if !m.hasSize(offset, byteCount) {
+		return nil, false
+	}
+	return m[offset : offset+byteCount : offset+byteCount], true
+}
+
+func (m mockMemory) WriteByte(offset uint32, v byte) bool {
+	if offset >= m.Size() {
+		return false
+	}
+	m[offset] = v
+	return true
+}
+
+func (m mockMemory) WriteUint16Le(offset uint32, v uint16) bool {
+	if !m.hasSize(offset, 2) {
+		return false
+	}
+	binary.LittleEndian.PutUint16(m[offset:], v)
+	return true
+}
+
+func (m mockMemory) WriteUint32Le(offset, v uint32) bool {
+	if !m.hasSize(offset, 4) {
+		return false
+	}
+	binary.LittleEndian.PutUint32(m[offset:], v)
+	return true
+}
+
+func (m mockMemory) WriteFloat32Le(offset uint32, v float32) bool {
+	return m.WriteUint32Le(offset, math.Float32bits(v))
+}
+
+func (m mockMemory) WriteUint64Le(offset uint32, v uint64) bool {
+	if !m.hasSize(offset, 8) {
+		return false
+	}
+	binary.LittleEndian.PutUint64(m[offset:], v)
+	return true
+}
+
+func (m mockMemory) WriteFloat64Le(offset uint32, v float64) bool {
+	return m.WriteUint64Le(offset, math.Float64bits(v))
+}
+
+func (m mockMemory) Write(offset uint32, val []byte) bool {
+	if !m.hasSize(offset, uint32(len(val))) {
+		return false
+	}
+	copy(m[offset:], val)
+	return true
+}
+
+func (m mockMemory) WriteString(offset uint32, val string) bool {
+	if !m.hasSize(offset, uint32(len(val))) {
+		return false
+	}
+	copy(m[offset:], val)
+	return true
+}
+
+func (m *mockMemory) Grow(delta uint32) (result uint32, ok bool) {
+	prev := (len(*m) + 65535) / 65536
+	*m = append(*m, make([]byte, 65536*delta)...)
+	return uint32(prev), true
+}
+
+func (m mockMemory) PageSize() (result uint32) {
+	return uint32(len(m) / 65536)
+}
+
+func (m mockMemory) hasSize(offset uint32, byteCount uint32) bool {
+	return uint64(offset)+uint64(byteCount) <= uint64(len(m))
+}
diff --git a/stmt.go b/stmt.go
index 7f1d93e..419c295 100644
--- a/stmt.go
+++ b/stmt.go
@@ -15,6 +15,8 @@ type Stmt struct {
 
 // Close destroys the prepared statement object.
 //
+// It is safe to close a nil, zero or closed prepared statement.
+//
 // https://www.sqlite.org/c3ref/finalize.html
 func (s *Stmt) Close() error {
 	if s == nil || s.handle == 0 {
diff --git a/util.go b/util.go
new file mode 100644
index 0000000..7a5bf13
--- /dev/null
+++ b/util.go
@@ -0,0 +1,16 @@
+package sqlite3
+
+// Return true if stmt is an empty SQL statement.
+// This is used as an optimization.
+// It's OK to always return false here.
+func emptyStatement(stmt string) bool {
+	for _, b := range []byte(stmt) {
+		switch b {
+		case ' ', '\n', '\r', '\t', '\v', '\f':
+		case ';':
+		default:
+			return false
+		}
+	}
+	return true
+}
diff --git a/util_test.go b/util_test.go
index fcb5ccc..48e6b95 100644
--- a/util_test.go
+++ b/util_test.go
@@ -1,161 +1,54 @@
 package sqlite3
 
 import (
-	"context"
-	"encoding/binary"
-	"math"
-
-	"github.com/tetratelabs/wazero/api"
+	"testing"
 )
 
-func init() {
-	Path = "./embed/sqlite3.wasm"
-}
-
-func newMemory(size uint32) memory {
-	mem := make(mockMemory, size)
-	return memory{mockModule{&mem}}
-}
-
-type mockModule struct {
-	memory api.Memory
-}
-
-func (m mockModule) Memory() api.Memory { return m.memory }
-func (m mockModule) String() string     { return "mockModule" }
-func (m mockModule) Name() string       { return "mockModule" }
-
-func (m mockModule) ExportedGlobal(name string) api.Global                          { return nil }
-func (m mockModule) ExportedMemory(name string) api.Memory                          { return nil }
-func (m mockModule) ExportedFunction(name string) api.Function                      { return nil }
-func (m mockModule) ExportedMemoryDefinitions() map[string]api.MemoryDefinition     { return nil }
-func (m mockModule) ExportedFunctionDefinitions() map[string]api.FunctionDefinition { return nil }
-func (m mockModule) CloseWithExitCode(ctx context.Context, exitCode uint32) error   { return nil }
-func (m mockModule) Close(context.Context) error                                    { return nil }
-
-type mockMemory []byte
-
-func (m mockMemory) Definition() api.MemoryDefinition { return nil }
-
-func (m mockMemory) Size() uint32 { return uint32(len(m)) }
-
-func (m mockMemory) ReadByte(offset uint32) (byte, bool) {
-	if offset >= m.Size() {
-		return 0, false
+func Test_emptyStatement(t *testing.T) {
+	tests := []struct {
+		name string
+		stmt string
+		want bool
+	}{
+		{"empty", "", true},
+		{"space", " ", true},
+		{"separator", ";\n ", true},
+		{"begin", "BEGIN", false},
+		{"select", "SELECT 1;", false},
 	}
-	return m[offset], true
-}
-
-func (m mockMemory) ReadUint16Le(offset uint32) (uint16, bool) {
-	if !m.hasSize(offset, 2) {
-		return 0, false
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := emptyStatement(tt.stmt); got != tt.want {
+				t.Errorf("emptyStatement(%q) = %v, want %v", tt.stmt, got, tt.want)
+			}
+		})
 	}
-	return binary.LittleEndian.Uint16(m[offset : offset+2]), true
 }
 
-func (m mockMemory) ReadUint32Le(offset uint32) (uint32, bool) {
-	if !m.hasSize(offset, 4) {
-		return 0, false
+func Fuzz_emptyStatement(f *testing.F) {
+	f.Add("")
+	f.Add(" ")
+	f.Add(";\n ")
+	f.Add("BEGIN")
+	f.Add("SELECT 1;")
+
+	db, err := Open(":memory:")
+	if err != nil {
+		f.Fatal(err)
 	}
-	return binary.LittleEndian.Uint32(m[offset : offset+4]), true
-}
+	defer db.Close()
 
-func (m mockMemory) ReadFloat32Le(offset uint32) (float32, bool) {
-	v, ok := m.ReadUint32Le(offset)
-	if !ok {
-		return 0, false
-	}
-	return math.Float32frombits(v), true
-}
-
-func (m mockMemory) ReadUint64Le(offset uint32) (uint64, bool) {
-	if !m.hasSize(offset, 8) {
-		return 0, false
-	}
-	return binary.LittleEndian.Uint64(m[offset : offset+8]), true
-}
-
-func (m mockMemory) ReadFloat64Le(offset uint32) (float64, bool) {
-	v, ok := m.ReadUint64Le(offset)
-	if !ok {
-		return 0, false
-	}
-	return math.Float64frombits(v), true
-}
-
-func (m mockMemory) Read(offset, byteCount uint32) ([]byte, bool) {
-	if !m.hasSize(offset, byteCount) {
-		return nil, false
-	}
-	return m[offset : offset+byteCount : offset+byteCount], true
-}
-
-func (m mockMemory) WriteByte(offset uint32, v byte) bool {
-	if offset >= m.Size() {
-		return false
-	}
-	m[offset] = v
-	return true
-}
-
-func (m mockMemory) WriteUint16Le(offset uint32, v uint16) bool {
-	if !m.hasSize(offset, 2) {
-		return false
-	}
-	binary.LittleEndian.PutUint16(m[offset:], v)
-	return true
-}
-
-func (m mockMemory) WriteUint32Le(offset, v uint32) bool {
-	if !m.hasSize(offset, 4) {
-		return false
-	}
-	binary.LittleEndian.PutUint32(m[offset:], v)
-	return true
-}
-
-func (m mockMemory) WriteFloat32Le(offset uint32, v float32) bool {
-	return m.WriteUint32Le(offset, math.Float32bits(v))
-}
-
-func (m mockMemory) WriteUint64Le(offset uint32, v uint64) bool {
-	if !m.hasSize(offset, 8) {
-		return false
-	}
-	binary.LittleEndian.PutUint64(m[offset:], v)
-	return true
-}
-
-func (m mockMemory) WriteFloat64Le(offset uint32, v float64) bool {
-	return m.WriteUint64Le(offset, math.Float64bits(v))
-}
-
-func (m mockMemory) Write(offset uint32, val []byte) bool {
-	if !m.hasSize(offset, uint32(len(val))) {
-		return false
-	}
-	copy(m[offset:], val)
-	return true
-}
-
-func (m mockMemory) WriteString(offset uint32, val string) bool {
-	if !m.hasSize(offset, uint32(len(val))) {
-		return false
-	}
-	copy(m[offset:], val)
-	return true
-}
-
-func (m *mockMemory) Grow(delta uint32) (result uint32, ok bool) {
-	prev := (len(*m) + 65535) / 65536
-	*m = append(*m, make([]byte, 65536*delta)...)
-	return uint32(prev), true
-}
-
-func (m mockMemory) PageSize() (result uint32) {
-	return uint32(len(m) / 65536)
-}
-
-func (m mockMemory) hasSize(offset uint32, byteCount uint32) bool {
-	return uint64(offset)+uint64(byteCount) <= uint64(len(m))
+	f.Fuzz(func(t *testing.T, sql string) {
+		// If empty, SQLite parses it as empty.
+		if emptyStatement(sql) {
+			stmt, _, err := db.Prepare(sql)
+			if err != nil {
+				t.Error(err)
+			}
+			if stmt != nil {
+				t.Error(stmt)
+			}
+			stmt.Close()
+		}
+	})
 }