diff --git a/internal/wasm/memory.go b/internal/wasm/memory.go
index c882b0f0..e2d994f9 100644
--- a/internal/wasm/memory.go
+++ b/internal/wasm/memory.go
@@ -111,7 +111,7 @@ func (m *MemoryInstance) ReadFloat64Le(offset uint32) (float64, bool) {
 
 // Read implements the same method as documented on api.Memory.
 func (m *MemoryInstance) Read(offset, byteCount uint32) ([]byte, bool) {
-	if !m.hasSize(offset, byteCount) {
+	if !m.hasSize(offset, uint64(byteCount)) {
 		return nil, false
 	}
 	return m.Buffer[offset : offset+byteCount : offset+byteCount], true
@@ -157,7 +157,7 @@ func (m *MemoryInstance) WriteFloat64Le(offset uint32, v float64) bool {
 
 // Write implements the same method as documented on api.Memory.
 func (m *MemoryInstance) Write(offset uint32, val []byte) bool {
-	if !m.hasSize(offset, uint32(len(val))) {
+	if !m.hasSize(offset, uint64(len(val))) {
 		return false
 	}
 	copy(m.Buffer[offset:], val)
@@ -166,7 +166,7 @@ func (m *MemoryInstance) Write(offset uint32, val []byte) bool {
 
 // WriteString implements the same method as documented on api.Memory.
 func (m *MemoryInstance) WriteString(offset uint32, val string) bool {
-	if !m.hasSize(offset, uint32(len(val))) {
+	if !m.hasSize(offset, uint64(len(val))) {
 		return false
 	}
 	copy(m.Buffer[offset:], val)
@@ -243,8 +243,8 @@ func (m *MemoryInstance) size() uint32 {
 // hasSize returns true if Len is sufficient for byteCount at the given offset.
 //
 // Note: This is always fine, because memory can grow, but never shrink.
-func (m *MemoryInstance) hasSize(offset uint32, byteCount uint32) bool {
-	return uint64(offset)+uint64(byteCount) <= uint64(len(m.Buffer)) // uint64 prevents overflow on add
+func (m *MemoryInstance) hasSize(offset uint32, byteCount uint64) bool {
+	return uint64(offset)+byteCount <= uint64(len(m.Buffer)) // uint64 prevents overflow on add
 }
 
 // readUint32Le implements ReadUint32Le without using a context. This is extracted as both ints and floats are stored in
diff --git a/internal/wasm/memory_test.go b/internal/wasm/memory_test.go
index 832b2e45..5957741d 100644
--- a/internal/wasm/memory_test.go
+++ b/internal/wasm/memory_test.go
@@ -2,8 +2,10 @@ package wasm
 
 import (
 	"math"
+	"reflect"
 	"strings"
 	"testing"
+	"unsafe"
 
 	"github.com/tetratelabs/wazero/api"
 	"github.com/tetratelabs/wazero/internal/testing/require"
@@ -194,7 +196,7 @@ func TestMemoryInstance_HasSize(t *testing.T) {
 		tc := tt
 
 		t.Run(tc.name, func(t *testing.T) {
-			require.Equal(t, tc.expected, memory.hasSize(tc.offset, uint32(tc.sizeInBytes)))
+			require.Equal(t, tc.expected, memory.hasSize(tc.offset, tc.sizeInBytes))
 		})
 	}
 }
@@ -735,6 +737,23 @@ func TestMemoryInstance_Write(t *testing.T) {
 	require.False(t, ok)
 }
 
+func TestMemoryInstance_Write_overflow(t *testing.T) {
+	mem := &MemoryInstance{Buffer: []byte{0, 0, 0, 0, 16, 0, 0, 0}, Min: 1}
+
+	// Test overflow
+	huge := uint64(math.MaxUint32 + 1 + 4)
+	if huge != uint64(int(huge)) {
+		t.Skip("Skipping on 32-bit")
+	}
+
+	buf := []byte{16, 0, 0, 4}
+	header := (*reflect.SliceHeader)(unsafe.Pointer(&buf))
+	header.Len = int(huge)
+	header.Cap = int(huge)
+
+	require.False(t, mem.Write(4, buf))
+}
+
 func TestMemoryInstance_WriteString(t *testing.T) {
 	mem := &MemoryInstance{Buffer: []byte{0, 0, 0, 0, 16, 0, 0, 0}, Min: 1}