quote the defines
diff --git a/frontend_server_client/lib/src/frontend_server_client.dart b/frontend_server_client/lib/src/frontend_server_client.dart
index 3ab906d..58ef6df 100644
--- a/frontend_server_client/lib/src/frontend_server_client.dart
+++ b/frontend_server_client/lib/src/frontend_server_client.dart
@@ -100,7 +100,8 @@
         nativeAssets,
       ],
       if (dartDefines != null) ...[
-        for (var entry in dartDefines.entries) '-D=${entry.key}=${entry.value}',
+        for (var entry in dartDefines.entries)
+          '-D="${entry.key}=${entry.value}"',
       ],
     ];
     late final Process feServer;