diff --git a/nixos/modules/services/databases/foundationdb.nix b/nixos/modules/services/databases/foundationdb.nix
index ad24f9f4b0f..1505f92e751 100644
--- a/nixos/modules/services/databases/foundationdb.nix
+++ b/nixos/modules/services/databases/foundationdb.nix
@@ -35,6 +35,7 @@ let
     ${optionalString (cfg.class != null) "class = ${cfg.class}"}
     memory         = ${cfg.memory}
     storage_memory = ${cfg.storageMemory}
+    trace_format   = ${cfg.traceFormat}
 
     ${optionalString (cfg.tls != null) ''
       tls_plugin           = ${pkg}/libexec/plugins/FDBLibTLS.so
@@ -317,6 +318,12 @@ in
       default     = "/run/foundationdb.pid";
       description = "Path to pidfile for fdbmonitor.";
     };
+
+    traceFormat = mkOption {
+      type = types.enum [ "xml" "json" ];
+      default = "xml";
+      description = "Trace logging format.";
+    };
   };
 
   config = mkIf cfg.enable {