diff --git a/lib/fizzy/parser_expr.cpp b/lib/fizzy/parser_expr.cpp
index a7a50798d5..dd8c25f1f1 100644
--- a/lib/fizzy/parser_expr.cpp
+++ b/lib/fizzy/parser_expr.cpp
@@ -20,7 +20,7 @@ inline void store(uint8_t* dst, T value) noexcept
 }
 
 template <typename T>
-inline void push(std::vector<uint8_t>& b, T value)
+inline void push(bytes& b, T value)
 {
     uint8_t storage[sizeof(T)];
     store(storage, value);
@@ -198,8 +198,7 @@ inline void update_branch_stack(const ControlFrame& current_frame, const Control
         drop_operand(current_frame, operand_stack, from_valtype(*branch_frame_type));
 }
 
-void push_branch_immediates(
-    const ControlFrame& branch_frame, int stack_height, std::vector<uint8_t>& instructions)
+void push_branch_immediates(const ControlFrame& branch_frame, int stack_height, bytes& instructions)
 {
     // How many stack items to drop when taking the branch.
     const auto stack_drop = stack_height - branch_frame.parent_stack_height;
@@ -872,7 +871,7 @@ parser_result<Code> parse_expr(const uint8_t* pos, const uint8_t* end, FuncIdx f
             break;
         }
         }
-        code.instructions.emplace_back(opcode);
+        code.instructions.push_back(opcode);
     }
     assert(control_stack.empty());
     return {code, pos};
diff --git a/lib/fizzy/types.hpp b/lib/fizzy/types.hpp
index 4485754142..bb25b6d5cd 100644
--- a/lib/fizzy/types.hpp
+++ b/lib/fizzy/types.hpp
@@ -362,7 +362,7 @@ struct Code
 
     // The instructions bytecode without immediate values.
     // https://webassembly.github.io/spec/core/binary/instructions.html
-    std::vector<uint8_t> instructions;
+    bytes instructions;
 };
 
 /// The reference to the `code` in the wasm binary.
diff --git a/test/unittests/execute_death_test.cpp b/test/unittests/execute_death_test.cpp
index 51539671bd..16b8bb6669 100644
--- a/test/unittests/execute_death_test.cpp
+++ b/test/unittests/execute_death_test.cpp
@@ -14,8 +14,8 @@ TEST(execute_death, malformed_instruction_opcode)
     constexpr uint8_t malformed_opcode = 6;
 
     Code code;
-    code.instructions.emplace_back(malformed_opcode);
-    code.instructions.emplace_back(static_cast<uint8_t>(Instr::end));
+    code.instructions.push_back(malformed_opcode);
+    code.instructions.push_back(static_cast<uint8_t>(Instr::end));
 
     auto module = std::make_unique<Module>();
     module->typesec.emplace_back(FuncType{});