diff --git a/embassy-usb/src/msos.rs b/embassy-usb/src/msos.rs
index 187b2ff8e..847338e5f 100644
--- a/embassy-usb/src/msos.rs
+++ b/embassy-usb/src/msos.rs
@@ -526,7 +526,7 @@ impl<'a> PropertyData<'a> {
             PropertyData::Binary(val) => val.len(),
             PropertyData::DwordLittleEndian(val) | PropertyData::DwordBigEndian(val) => core::mem::size_of_val(val),
             PropertyData::RegMultiSz(val) => {
-                core::mem::size_of::<u16>() * val.iter().map(|x| x.encode_utf16().count() + 1).sum::<usize>() + 1
+                core::mem::size_of::<u16>() * (val.iter().map(|x| x.encode_utf16().count() + 1).sum::<usize>() + 1)
             }
         }
     }