diff --git a/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.cpp b/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.cpp
index eb08889d251008947138ecd101666906655be9f8..758d2ddddde90f523d3e1139ca1bafd04b8f1850 100644
--- a/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.cpp
+++ b/Userland/Libraries/LibWasm/AbstractMachine/Interpreter.cpp
@@ -900,6 +900,11 @@ void BytecodeInterpreter::interpret(Configuration& configuration, InstructionPoi
     case Instructions::table_grow.value():
     case Instructions::table_size.value():
     case Instructions::table_fill.value():
+    case Instructions::i32_extend8_s.value():
+    case Instructions::i32_extend16_s.value():
+    case Instructions::i64_extend8_s.value():
+    case Instructions::i64_extend16_s.value():
+    case Instructions::i64_extend32_s.value():
     default:
     unimplemented:;
         dbgln("Instruction '{}' not implemented", instruction_name(instruction.opcode()));
diff --git a/Userland/Libraries/LibWasm/Opcode.h b/Userland/Libraries/LibWasm/Opcode.h
index 97d6ae6184b54f9cb4a98eacc0523073ef0376ac..b2b6ec3a2a1ba8bed58031f67fb10f2974a2a411 100644
--- a/Userland/Libraries/LibWasm/Opcode.h
+++ b/Userland/Libraries/LibWasm/Opcode.h
@@ -187,6 +187,11 @@ static constexpr OpCode unreachable = 0x00,
                         i64_reinterpret_f64 = 0xbd,
                         f32_reinterpret_i32 = 0xbe,
                         f64_reinterpret_i64 = 0xbf,
+                        i32_extend8_s = 0xc0,
+                        i32_extend16_s = 0xc1,
+                        i64_extend8_s = 0xc2,
+                        i64_extend16_s = 0xc3,
+                        i64_extend32_s = 0xc4,
                         ref_null = 0xd0,
                         ref_is_null = 0xd1,
                         ref_func = 0xd2;
diff --git a/Userland/Libraries/LibWasm/Parser/Parser.cpp b/Userland/Libraries/LibWasm/Parser/Parser.cpp
index 43c9a9826390512add07cb14ef2d614c7edcd0fc..797e9367dcf039f2458f5c0def83f8d8302f6b7f 100644
--- a/Userland/Libraries/LibWasm/Parser/Parser.cpp
+++ b/Userland/Libraries/LibWasm/Parser/Parser.cpp
@@ -631,6 +631,11 @@ ParseResult<Vector<Instruction>> Instruction::parse(InputStream& stream, Instruc
     case Instructions::i64_reinterpret_f64.value():
     case Instructions::f32_reinterpret_i32.value():
     case Instructions::f64_reinterpret_i64.value():
+    case Instructions::i32_extend8_s.value():
+    case Instructions::i32_extend16_s.value():
+    case Instructions::i64_extend8_s.value():
+    case Instructions::i64_extend16_s.value():
+    case Instructions::i64_extend32_s.value():
         return Vector { Instruction { opcode } };
     case 0xfc: {
         // These are multibyte instructions.
diff --git a/Userland/Libraries/LibWasm/Printer/Printer.cpp b/Userland/Libraries/LibWasm/Printer/Printer.cpp
index 0fb8ff44121d93bd3c9856dd942bee4460f687a7..e720d61fbd59787603784117d1a50f39264694b5 100644
--- a/Userland/Libraries/LibWasm/Printer/Printer.cpp
+++ b/Userland/Libraries/LibWasm/Printer/Printer.cpp
@@ -798,6 +798,11 @@ HashMap<Wasm::OpCode, String> Wasm::Names::instruction_names {
     { Instructions::i64_reinterpret_f64, "i64.reinterpret.f64" },
     { Instructions::f32_reinterpret_i32, "f32.reinterpret.i32" },
     { Instructions::f64_reinterpret_i64, "f64.reinterpret.i64" },
+    { Instructions::i32_extend8_s, "i32.extend8_s" },
+    { Instructions::i32_extend16_s, "i32.extend16_s" },
+    { Instructions::i64_extend8_s, "i64.extend8_s" },
+    { Instructions::i64_extend16_s, "i64.extend16_s" },
+    { Instructions::i64_extend32_s, "i64.extend32_s" },
     { Instructions::ref_null, "ref.null" },
     { Instructions::ref_is_null, "ref.is.null" },
     { Instructions::ref_func, "ref.func" },