diff --git a/compiler/generator.cc b/compiler/generator.cc
index 1dc981b..fa4b6f7 100644
--- a/compiler/generator.cc
+++ b/compiler/generator.cc
@@ -6,6 +6,9 @@
 #include <iomanip>
 
 namespace ceos {
+  static unsigned lookupID = 1;
+  static bool capturesScope = true;
+
   std::stringstream &Generator::generate() {
     generateProgram(m_ast);
     emitOpcode(Opcode::exit);
@@ -103,6 +106,11 @@ namespace ceos {
     } else {
       emitOpcode(Opcode::lookup);
       write(id->uid);
+      if (capturesScope) {
+        write(0);
+      } else {
+        write(lookupID++);
+      }
     }
   }
 
@@ -155,6 +163,7 @@ namespace ceos {
       }
     };
 
+    capturesScope = fn->body->capturesScope;
     generateNode(fn->body);
 
     emitOpcode(Opcode::ret);
@@ -205,6 +214,7 @@ namespace ceos {
 
     write(Section::Header);
     write(Section::Text);
+    write(lookupID);
     m_output << text;
   }
 
@@ -326,6 +336,7 @@ section_functions: {
     }
 
 section_code:
+    bytecode.seekg(4, bytecode.cur);
     while (true) {
       char opcode = bytecode.get();
       if (bytecode.eof() || bytecode.fail()) {
@@ -358,7 +369,8 @@ section_functions: {
       }
       case Opcode::lookup: {
         READ_INT(bytecode, id);
-        WRITE(5, "lookup $" << id << "(" << strings[id] << ")");
+        READ_INT(bytecode, cacheSlot);
+        WRITE(9, "lookup $" << id << "(" << strings[id] << ") [cacheSlot=" << cacheSlot << "]");
         break;
       }
       case Opcode::create_closure: {
diff --git a/compiler/interpreter.S b/compiler/interpreter.S
index 2954c66..5bfede2 100644
--- a/compiler/interpreter.S
+++ b/compiler/interpreter.S
@@ -4,10 +4,13 @@
 #define STRINGS r13
 #define VM r14
 #define BCBASE r15
+#define LOOKUP rbx
 
 .macro read
 .if $0 == 1
   mov 0x1(%BYTECODE), $1
+.elseif $0 == 2
+  mov 0x5(%BYTECODE), $1
 .else
   mov $$$0, %rax
   mov -0x3(%BYTECODE, %rax, 4), $1
@@ -57,11 +60,13 @@ _execute:
   push %STRINGS
   push %VM
   push %BCBASE
+  push %LOOKUP
   mov %rsp, %rbp
   mov %rdi, %BYTECODE
   mov %rsi, %STRINGS
   mov %rdx, %VM
   mov %rcx, %BCBASE
+  mov %r8,  %LOOKUP
 
 _loop:
   xor %rax, %rax
@@ -88,6 +93,7 @@ _loop_op_addresses:
 
 _op_exit:
   mov %rbp, %rsp
+  pop %LOOKUP
   pop %BCBASE
   pop %VM
   pop %STRINGS
@@ -101,20 +107,29 @@ _op_push:
   skip 1
 
 _op_lookup:
+_op_lookup_fast_path:
+  read 2, %edi
+  mov (%LOOKUP, %rdi, 8), %rsi // Cached address
+  test %rsi, %rsi
+  jz _op_lookup_slow_path
+  push %rsi
+  skip 2
+
+_op_lookup_slow_path:
   read 1, %esi // string ID
-  mov (%STRINGS, %rsi, 8), %rsi // actual char *
   mov (%VM), %r9 // VM::m_scope *
+  mov (%STRINGS, %rsi, 8), %rsi // actual char *
 
-load:
+_op_lookup_load:
   mov (%r9), %rax // Scope::table *
   test %rax, %rax
-  jz check_parent
+  jz _op_lookup_check_parent
   mov 0x18(%r9), %edx // Scope::tableHash
   mov %esi, %ecx // index
   and %edx, %ecx // index &= hash
   mov %ecx, %r8d // begin
 
-begin:
+_op_lookup_begin:
   mov %ecx, %edi
   shl $1, %edi
   mov (%rax, %rdi, 0x8), %r11  // Entry::key
@@ -125,22 +140,35 @@ begin:
   skip 1
 
 slow_path:
+  cmp %rsi, %r11
+  jz _op_lookup_found
   test %r11,%r11
-  jz check_parent
+  jz _op_lookup_check_parent
   inc %ecx
   and %edx, %ecx
   cmp %ecx, %r8d
-  jnz begin
+  jnz _op_lookup_begin
 
-check_parent:
+_op_lookup_check_parent:
   mov 0x8(%r9), %r9 // Scope::parent
   test %r9, %r9
-  jnz load
+  jnz _op_lookup_load
 
-not_found:
+_op_lookup_not_found:
   mov %rsi, %rdi
   ccall _symbolNotFound
 
+_op_lookup_found:
+  mov 0x8(%rax, %rdi, 0x8), %rax  // Entry::value
+  read 2, %edx
+  test %edx, %edx
+  jz _op_lookup_done
+  mov %rax, (%LOOKUP, %rdx, 8) // cache value
+
+_op_lookup_done:
+  push %rax
+  skip 2
+
 _op_call:
   // pop the callee from the stack
   pop %rcx
diff --git a/compiler/vm.cc b/compiler/vm.cc
index 4a84cef..ae8dd7f 100644
--- a/compiler/vm.cc
+++ b/compiler/vm.cc
@@ -11,7 +11,8 @@ extern "C" void execute(
     const uint8_t *bytecode,
     String *stringTable,
     VM *vm,
-    const uint8_t *bcbase);
+    const uint8_t *bcbase,
+    void *lookupTable);
 
 extern "C" void setScope(VM *vm, const char *name, Value value);
 void setScope(VM *vm, const char *name, Value value) {
@@ -41,7 +42,7 @@ uint64_t createClosure(VM *vm, unsigned fnID, bool capturesScope) {
 
 extern "C" unsigned prepareClosure(unsigned argc, Value *argv, VM *vm, Closure *closure);
 unsigned prepareClosure(__unused unsigned argc, __unused Value *argv, VM *vm, Closure *closure) {
-  if (closure->scope) {
+  if (closure->scope != NULL) {
     vm->m_scope = vm->m_scope->create(closure->scope);
   }
   return closure->fn->offset;
@@ -55,7 +56,7 @@ void finishClosure(VM *vm, Closure *closure) {
 }
 
 extern "C" void symbolNotFound(char *);
-extern "C" void symbolNotFound(char *symbolName) {
+void symbolNotFound(char *symbolName) {
   fprintf(stderr, "Symbol not found: %s\n", symbolName);
   throw;
 }
@@ -80,9 +81,12 @@ extern "C" void symbolNotFound(char *symbolName) {
         case Section::Functions:
           loadFunctions();
           break;
-        case Section::Text:
-          ::ceos::execute(m_bytecode + pc, m_stringTable.data(), this, m_bytecode);
+        case Section::Text: {
+          auto lookupTableSize = read<unsigned>();
+          void *lookupTable = calloc(lookupTableSize * 8, 1);
+          ::ceos::execute(m_bytecode + pc, m_stringTable.data(), this, m_bytecode, lookupTable);
           return;
+        }
         default:
           std::cerr << "Unknown section: `0x0" << std::hex << section << "`\n";
           throw;
@@ -90,7 +94,7 @@ extern "C" void symbolNotFound(char *symbolName) {
     }
   }
 
-  void VM::loadStrings() {
+  inline void VM::loadStrings() {
     while (true) {
       auto header = read<unsigned>();
 
@@ -104,7 +108,7 @@ extern "C" void symbolNotFound(char *symbolName) {
     }
   }
 
-  void VM::loadFunctions() {
+  inline void VM::loadFunctions() {
     auto initialHeader = read<unsigned>();
     assert(initialHeader == Section::FunctionHeader);