diff --git a/src/parser.rs b/src/parser.rs
index 5df5332..433ff61 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -1943,7 +1943,10 @@ fn parse_file_attribute(line: Chars) -> Result<FileAttribute, ContentError> {
             args.first().map(|value| parse_ident(value)).transpose()?,
         )),
         (".CreationDate", args, 1) => Ok(FileAttribute::CreationDate(parse_date_time(args[0])?)),
-        (".GenerationSoftware", args, len) if len <= 3 => {
+        // Vendor and application are mandatory; anything shorter falls
+        // through to a user-defined attribute instead of indexing past the
+        // arguments.
+        (".GenerationSoftware", args, len) if (2..=3).contains(&len) => {
             Ok(FileAttribute::GenerationSoftware(GenerationSoftware {
                 vendor: args[0].to_string(),
                 application: args[1].to_string(),
diff --git a/tests/component_tests.rs b/tests/component_tests.rs
index 919ceea..2d6b2b1 100644
--- a/tests/component_tests.rs
+++ b/tests/component_tests.rs
@@ -4055,3 +4055,24 @@ fn malformed_aperture_definition() {
         } if type_str.eq("T") && content.eq("%ADD10T*%")
     ));
 }
+
+/// A `.GenerationSoftware` file attribute with fewer than the mandatory vendor and
+/// application values must not panic; it is kept as a user-defined attribute.
+#[test]
+fn generation_software_with_one_value_does_not_panic() {
+    // given
+    logging_init();
+
+    let reader = gerber_to_reader("%FSLAX23Y23*%\n%MOMM*%\n%TF.GenerationSoftware,KiCad*%\nM02*\n");
+
+    // when
+    let doc = parse(reader).unwrap();
+
+    // then
+    assert!(doc.commands.iter().any(|c| matches!(
+        c,
+        Ok(Command::ExtendedCode(ExtendedCode::FileAttribute(
+            FileAttribute::UserDefined { name, .. }
+        ))) if name == ".GenerationSoftware"
+    )));
+}