diff --git a/libc/runtime/stack.h b/libc/runtime/stack.h
index bd4525ea9..f3f6e618a 100644
--- a/libc/runtime/stack.h
+++ b/libc/runtime/stack.h
@@ -121,6 +121,13 @@ extern char ape_stack_align[] __attribute__((__weak__));
     vAddr;                                      \
   })
 
+/**
+ * Returns true if at least `n` bytes of stack are available.
+ */
+#define HaveStackMemory(n) \
+  (IsTiny() ||             \
+   (intptr_t)__builtin_frame_address(0) >= GetStackAddr() + PAGESIZE * (n))
+
 COSMOPOLITAN_C_END_
 #endif /* GNU ELF */
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
diff --git a/test/tool/net/ljson_test.lua b/test/tool/net/ljson_test.lua
index e15c569eb..dc0873db8 100644
--- a/test/tool/net/ljson_test.lua
+++ b/test/tool/net/ljson_test.lua
@@ -124,9 +124,6 @@ res, err = DecodeJson([[
 {"k":{"k":{"k":{"k":0}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}
 }}}}}}}}}
 ]])
-if not res then
-   print('wut', err)
-end
 assert(res)
 
 -- 64 objects
diff --git a/third_party/lua/luaencodejsondata.c b/third_party/lua/luaencodejsondata.c
index 8dd4910e4..315c44728 100644
--- a/third_party/lua/luaencodejsondata.c
+++ b/third_party/lua/luaencodejsondata.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
 #include "libc/bits/bits.h"
+#include "libc/bits/likely.h"
 #include "libc/fmt/itoa.h"
 #include "libc/intrin/kprintf.h"
 #include "libc/log/log.h"
@@ -165,7 +166,7 @@ static int SerializeTable(lua_State *L, char **buf, int idx,
   int rc;
   bool isarray;
   lua_Unsigned n;
-  if ((intptr_t)__builtin_frame_address(0) < GetStackAddr() + PAGESIZE * 2) {
+  if (UNLIKELY(!HaveStackMemory(PAGESIZE))) {
     z->reason = "out of stack";
     return -1;
   }
diff --git a/third_party/lua/luaencodeluadata.c b/third_party/lua/luaencodeluadata.c
index b66d3e9ea..f26e8421d 100644
--- a/third_party/lua/luaencodeluadata.c
+++ b/third_party/lua/luaencodeluadata.c
@@ -336,7 +336,7 @@ static int SerializeTable(lua_State *L, char **buf, int idx,
                           struct Serializer *z, int depth) {
   int rc;
   intptr_t rsp, bot;
-  if ((intptr_t)__builtin_frame_address(0) < GetStackAddr() + PAGESIZE * 2) {
+  if (UNLIKELY(!HaveStackMemory(PAGESIZE))) {
     z->reason = "out of stack";
     return -1;
   }
diff --git a/tool/net/ljson.c b/tool/net/ljson.c
index fa1f5ecaf..cddbbbee1 100644
--- a/tool/net/ljson.c
+++ b/tool/net/ljson.c
@@ -50,8 +50,7 @@ static struct DecodeJson Parse(struct lua_State *L, const char *p,
   if (UNLIKELY(!depth)) {
     return (struct DecodeJson){-1, "maximum depth exceeded"};
   }
-  if (UNLIKELY((intptr_t)__builtin_frame_address(0) <
-               GetStackAddr() + PAGESIZE * 2)) {
+  if (UNLIKELY(!HaveStackMemory(PAGESIZE))) {
     return (struct DecodeJson){-1, "out of stack"};
   }
   for (a = p, d = +1; p < e;) {