diff --git a/.gitignore b/.gitignore
index 7050af6..a9bc1ab 100644
--- a/.gitignore
+++ b/.gitignore
@@ -38,3 +38,7 @@ sdkconfig.old
 # Third-party working copies kept beside the project, not part of it. The ASN.1
 # modules this project actually needs are vendored under asn1/ instead.
 /C-ITS-Parser/
+
+# Office lock files. Word/Excel create these beside a document while it is open
+# and remove them on close, so they are transient and machine-local.
+~$*