diff --git a/rvgo/fast/memory.go b/rvgo/fast/memory.go
index e239fcdd..0b65aa75 100644
--- a/rvgo/fast/memory.go
+++ b/rvgo/fast/memory.go
@@ -128,7 +128,7 @@ func (m *Memory) SetUnaligned(addr uint64, dat []byte) {
 		m.Invalidate(addr) // invalidate this branch of memory, now that the value changed
 	}
 
-	copy(p.Data[pageAddr:], dat)
+	copy(p.Data[pageAddr:], dat[d:])
 }
 
 func (m *Memory) GetUnaligned(addr uint64, dest []byte) {
diff --git a/rvgo/fast/memory_test.go b/rvgo/fast/memory_test.go
index 8653a6fc..9829ab96 100644
--- a/rvgo/fast/memory_test.go
+++ b/rvgo/fast/memory_test.go
@@ -412,3 +412,12 @@ func TestMemoryBinary(t *testing.T) {
 	m.GetUnaligned(8, dest[:])
 	require.Equal(t, uint8(123), dest[0])
 }
+
+func TestMemoryInvalidSetUnaligned(t *testing.T) {
+	t.Run("SetUnaligned incorrectly writes to next page", func(t *testing.T) {
+		m := NewMemory()
+		m.SetUnaligned(0x0FFE, []byte{0xaa, 0xbb, 0xcc, 0xdd})
+		require.Equal(t, m.pages[0].Data[4094:], []byte{0xaa, 0xbb})
+		require.Equal(t, m.pages[1].Data[0:2], []byte{0xcc, 0xdd})
+	})
+}