diff --git a/include/6502.hpp b/include/6502.hpp
index a423df7..92e1245 100644
--- a/include/6502.hpp
+++ b/include/6502.hpp
@@ -5,9 +5,6 @@
 
 struct mos6502 : ASMLine
 {
-
-
-
   enum class OpCode {
     unknown,
 
@@ -41,6 +38,8 @@ struct mos6502 : ASMLine
     ldy,
     lsr,
 
+    nop,
+
     ORA,
 
     pha,
@@ -92,6 +91,7 @@ struct mos6502 : ASMLine
     case OpCode::ldx:
     case OpCode::ldy:
     case OpCode::lsr:
+    case OpCode::nop:
     case OpCode::ORA:
     case OpCode::pha:
     case OpCode::php:
@@ -144,6 +144,7 @@ struct mos6502 : ASMLine
     case OpCode::ldx:
     case OpCode::ldy:
     case OpCode::lsr:
+    case OpCode::nop:
     case OpCode::ORA:
     case OpCode::pha:
     case OpCode::php:
@@ -229,6 +230,7 @@ struct mos6502 : ASMLine
     case OpCode::bpl: return "bpl";
     case OpCode::bcc: return "bcc";
     case OpCode::bcs: return "bcs";
+    case OpCode::nop: return "nop";
     case OpCode::unknown: return "";
     }
 
diff --git a/src/6502-c++.cpp b/src/6502-c++.cpp
index 77e1c39..f13e3f9 100644
--- a/src/6502-c++.cpp
+++ b/src/6502-c++.cpp
@@ -114,6 +114,8 @@ struct AVR : ASMLine
 
     mov,
 
+    nop,
+
     out,
 
     pop,
@@ -190,6 +192,7 @@ struct AVR : ASMLine
       if (o == "in") { return OpCode::in; }
       if (o == "out") { return OpCode::out; }
       if (o == "inc") { return OpCode::inc; }
+      if (o == "nop") { return OpCode::nop; }
     }
     }
     throw std::runtime_error(fmt::format("Unknown opcode: {}", o));
@@ -726,6 +729,10 @@ void translate_instruction(const Personality &personality,
       return;
     }
   }
+  case AVR::OpCode::nop: {
+    instructions.emplace_back(mos6502::OpCode::nop);
+    return;
+  }
   case AVR::OpCode::unknown: {
     throw std::runtime_error("Could not translate 'unknown' instruction");
   }
@@ -955,8 +962,8 @@ std::vector<mos6502> run(const Personality &personality, std::istream &input)
         try {
           i.text = new_labels.at(i.text);
         } catch (...) {
-          spdlog::error("Error looking up label name: '{}'", i.text);
-          throw;
+          spdlog::warn("Unused label: '{}', consider making function static until we remove unused functions", i.text);
+
         }
       }
     }
diff --git a/test/tests.cpp b/test/tests.cpp
index a4d7cc7..232947f 100644
--- a/test/tests.cpp
+++ b/test/tests.cpp
@@ -59,7 +59,7 @@ quit
 
 
   REQUIRE(system(fmt::format("{} -f {} -t C64 {}", mos6502_cpp_executable, source_filename, optimization_level).c_str()) == EXIT_SUCCESS);
-  REQUIRE(system(fmt::format("xvfb-run {} +saveres -warp -moncommands {}", x64_executable, vice_script_filename).c_str()) == EXIT_SUCCESS);
+  REQUIRE(system(fmt::format("xvfb-run -d {} +saveres -warp -moncommands {}", x64_executable, vice_script_filename).c_str()) == EXIT_SUCCESS);
 
   std::ifstream memory_dump(ram_dump_filename, std::ios::binary);
 
@@ -94,7 +94,7 @@ TEST_CASE("Can write to screen memory via function call")
     R"(
 
 void poke(unsigned int location, unsigned char value) {
-  *reinterpret_cast<volatile unsigned char *>(location) = 10;
+  *reinterpret_cast<volatile unsigned char *>(location) = value;
 }
 
 int main()
@@ -109,7 +109,7 @@ int main()
   const auto result = execute_c64_program("write_to_screen_memory_via_function", program, o_level, 0x400, 0x401);
 
   REQUIRE(result.size() == 2);
-  CHECK(result[0] == 10);
-  CHECK(result[0] == 11);
 
+    CHECK(result[0] == 10);
+    CHECK(result[1] == 11);
 }