diff --git a/aslp-cpp/.gitignore b/aslp-cpp/.gitignore
index b033b8d2..4a7cf188 100644
--- a/aslp-cpp/.gitignore
+++ b/aslp-cpp/.gitignore
@@ -11,3 +11,4 @@ CMakeUserPresets.json
 compile_commands.json
 env.bat
 env.ps1
+.cache
diff --git a/aslp-cpp/include/aslp-cpp/aslp-cpp.hpp b/aslp-cpp/include/aslp-cpp/aslp-cpp.hpp
index 7f367d4e..08feb239 100644
--- a/aslp-cpp/include/aslp-cpp/aslp-cpp.hpp
+++ b/aslp-cpp/include/aslp-cpp/aslp-cpp.hpp
@@ -14,7 +14,7 @@ class aslp_connection
 public:
   aslp_connection(const std::string& server_addr, int server_port);
   aslp_connection(aslp_connection&&) noexcept;
-  auto get_opcode(int opcode) -> std::string;
+  auto get_opcode(uint32_t opcode) -> std::string;
   void wait_active();
   ~aslp_connection();
 };
@@ -54,7 +54,7 @@ class aslp_client {
   auto static start(const std::string& addr, int server_port) -> std::unique_ptr<aslp_client>;
 
   /** Returns the semantics for the given opcode, as a newline-separated string. */
-  auto get_opcode(int opcode) -> std::string;
+  auto get_opcode(uint32_t opcode) -> std::string;
 
   /** Destroys the aslp_client and terminates the managed server as well. */
   virtual ~aslp_client() {
diff --git a/aslp-cpp/source/aslp-cpp.cpp b/aslp-cpp/source/aslp-cpp.cpp
index 03f51416..57cf5e75 100644
--- a/aslp-cpp/source/aslp-cpp.cpp
+++ b/aslp-cpp/source/aslp-cpp.cpp
@@ -147,7 +147,7 @@ void aslp_connection::wait_active()
   std::cout << "\n";
 }
 
-std::string aslp_connection::get_opcode(int opcode)
+std::string aslp_connection::get_opcode(uint32_t opcode)
 {
   auto codestr = std::format("{:#x}", opcode);
   std::cout << codestr << "\n";
@@ -165,7 +165,7 @@ std::string aslp_connection::get_opcode(int opcode)
     throw std::runtime_error(result["error"]);
   }
   if (!result.contains("semantics")) {
-    throw std::runtime_error(result["semantics missing"]);
+    throw std::runtime_error("semantics missing");
   }
   return result["semantics"];
 }
@@ -179,7 +179,7 @@ aslp_connection::aslp_connection(const std::string& server_addr,
 aslp_connection::aslp_connection(aslp_connection&&) noexcept = default;
 aslp_connection::~aslp_connection() = default;
 
-std::string aslp_client::get_opcode(int opcode)
+std::string aslp_client::get_opcode(uint32_t opcode)
 {
   aslp_connection conn {server_addr, server_port};
   conn.wait_active();