diff --git a/examples/server/server-common.cpp b/examples/server/server-common.cpp
index 8c3e8b23..2a0fdc5d 100644
--- a/examples/server/server-common.cpp
+++ b/examples/server/server-common.cpp
@@ -1202,8 +1202,11 @@ json anthropic_params_from_json(
         }
         else if (system_param.is_array()) {
             for (const auto& block : system_param) {
-                if (json_value(block, "type", std::string()) == "text") {
-                    system_content += json_value(block, "text", std::string());
+                 if (json_value(block, "type", std::string()) == "text") {
+                    std::string content_block = json_value(block, "text", std::string());
+                    if (!string_starts_with(content_block, "x-anthropic-")) {
+                        system_content += content_block;
+                    }
                 }
             }
         }