diff --git a/ueforth/common/core.h b/ueforth/common/core.h
index 4d05ed1..7c8589a 100644
--- a/ueforth/common/core.h
+++ b/ueforth/common/core.h
@@ -21,6 +21,7 @@
 #define CELL_ALIGNED(a) ((((cell_t) (a)) + CELL_MASK) & ~CELL_MASK)
 #define IMMEDIATE 1
 #define SMUDGE 2
+#define BUILTIN_FORK 4
 
 // Maximum ALSO layers.
 #define VOCABULARY_DEPTH 16
@@ -45,6 +46,7 @@ static struct {
   // Layout not used by Forth.
   cell_t *rp;  // spot to park main thread
   cell_t DOLIT_XT, DOFLIT_XT, DOEXIT_XT, YIELD_XT;
+  const BUILTIN_WORD *builtins;
 } g_sys;
 
 static cell_t convert(const char *pos, cell_t n, cell_t base, cell_t *ret) {
@@ -112,8 +114,15 @@ static cell_t find(const char *name, cell_t len) {
   for (cell_t ***voc = g_sys.context; *voc; ++voc) {
     cell_t xt = (cell_t) **voc;
     while (xt) {
-      if (!(*TOFLAGS(xt) & SMUDGE) && len == *TONAMELEN(xt) &&
-          same(name, TONAME(xt), len)) {
+      if ((*TOFLAGS(xt) & BUILTIN_FORK)) {
+        for (int i = 0; g_sys.builtins[i].name; ++i) {
+          if (len == g_sys.builtins[i].name_length &&
+              same(name, g_sys.builtins[i].name, len)) {
+            return (cell_t) &g_sys.builtins[i].code;
+          }
+        }
+      } else if (!(*TOFLAGS(xt) & SMUDGE) && len == *TONAMELEN(xt) &&
+                 same(name, TONAME(xt), len)) {
         return xt;
       }
       xt = *TOLINK(xt);
diff --git a/ueforth/common/forth_namespace_tests.fs b/ueforth/common/forth_namespace_tests.fs
index 30c3434..1035539 100644
--- a/ueforth/common/forth_namespace_tests.fs
+++ b/ueforth/common/forth_namespace_tests.fs
@@ -201,7 +201,6 @@ e: check-extra-opcodes
 
 e: check-core-opcodes
   out: ; 
-  out: foo 
   out: EXIT 
   out: : 
   out: IMMEDIATE 
diff --git a/ueforth/common/interp.h b/ueforth/common/interp.h
index 2e9fcf6..2e8d74f 100644
--- a/ueforth/common/interp.h
+++ b/ueforth/common/interp.h
@@ -19,19 +19,18 @@
 #define ADDR_DODOES && OP_DODOES
  
 static cell_t *forth_run(cell_t *init_rp) {
-  static const struct {
-    const char *name;
-    cell_t flags;
-    const void *code;
-  } foo[] = {
-#define XV(flags, name, op, code) name, flags, && OP_ ## op,
+  static const BUILTIN_WORD builtins[] = {
+#define XV(flags, name, op, code) \
+    name, 0, sizeof(name) - 1, (flags & 0xff), && OP_ ## op,
     PLATFORM_OPCODE_LIST
     EXTRA_OPCODE_LIST
     OPCODE_LIST
 #undef XV
+    0, 0, 0,
   };
 
   if (!init_rp) {
+    g_sys.builtins = builtins;
 #define XV(flags, name, op, code) create(name, sizeof(name) - 1, name[0] == ';', && OP_ ## op);
     PLATFORM_OPCODE_LIST
     EXTRA_OPCODE_LIST
diff --git a/ueforth/common/opcodes.h b/ueforth/common/opcodes.h
index d3465f3..2964852 100644
--- a/ueforth/common/opcodes.h
+++ b/ueforth/common/opcodes.h
@@ -61,6 +61,11 @@ typedef int64_t dcell_t;
 #endif
 
 enum { FORTH = 0, INTERNALS };
+typedef struct {
+  const char *name;
+  uint8_t flags, name_length, vocabulary;
+  const void *code;
+} BUILTIN_WORD;
 
 #define OPCODE_LIST \
   X("0=", ZEQUAL, tos = !tos ? -1 : 0) \
@@ -119,5 +124,4 @@ enum { FORTH = 0, INTERNALS };
                sp = evaluate1(sp, &tfp); \
                fp = tfp; w = *sp--; DROP; if (w) JMPW) \
   Y(EXIT, ip = (cell_t *) *rp--) \
-  Y(foo, DUP; tos = (cell_t) foo) \
   X(";", SEMICOLON, COMMA(g_sys.DOEXIT_XT); UNSMUDGE(); g_sys.state = 0)
diff --git a/ueforth/windows/interp.h b/ueforth/windows/interp.h
index bab906c..6d25c24 100644
--- a/ueforth/windows/interp.h
+++ b/ueforth/windows/interp.h
@@ -30,12 +30,9 @@ enum {
 };
 
 static cell_t *forth_run(cell_t *init_rp) {
-  static const struct {
-    const char *name;
-    cell_t flags;
-    const void *code;
-  } foo[] = {
-#define XV(flags, name, op, code) name, 0, (void *) OP_ ## op,
+  static const BUILTIN_WORD builtins[] = {
+#define XV(flags, name, op, code) \
+    name, 0, sizeof(name) - 1, (flags & 0xff), (void *) OP_ ## op,
     PLATFORM_OPCODE_LIST
     EXTRA_OPCODE_LIST
     OPCODE_LIST
@@ -43,6 +40,7 @@ static cell_t *forth_run(cell_t *init_rp) {
   };
 
   if (!init_rp) {
+    g_sys.builtins = builtins;
 #define XV(flags, name, op, code) \
     create(name, sizeof(name) - 1, name[0] == ';', (void *) OP_ ## op);
     PLATFORM_OPCODE_LIST