diff --git a/oximeter/oximeter/schema/switch-data-link.toml b/oximeter/oximeter/schema/switch-data-link.toml
index 8fb8f2f108..d6744e8c7f 100644
--- a/oximeter/oximeter/schema/switch-data-link.toml
+++ b/oximeter/oximeter/schema/switch-data-link.toml
@@ -173,6 +173,15 @@ versions = [
     { added_in = 1, fields = [ "port_id", "link_id" ] }
 ]
 
+[[metrics]]
+name = "pcs_sync_loss"
+description = "Total number of times PCS sync was lost on the data link"
+units = "count"
+datum_type = "cumulative_u64"
+versions = [
+    { added_in = 1, fields = [ "port_id", "link_id" ] }
+]
+
 [[metrics]]
 name = "fec_high_symbol_errors"
 description = "FEC symbol error threshold exceeded"