diff --git a/.clang-format b/.clang-format
index 9b3aa8b..5aa5600 100644
--- a/.clang-format
+++ b/.clang-format
@@ -1 +1,2 @@
 BasedOnStyle: LLVM
+SortIncludes: Never
diff --git a/src/buffer.c b/src/buffer.c
index b9c449f..21b2253 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -1,16 +1,9 @@
 /* buffer.c — fixed-capacity byte buffer */
 
 #include "buffer.h"
+#include "mem.h"
 #include "utf8.h"
 
-typedef __SIZE_TYPE__ size_t;
-
-void *memcpy(void *dst, const void *src, size_t n) {
-  return __builtin_memcpy(dst, src, n);
-}
-
-void *memset(void *dst, int c, size_t n) { return __builtin_memset(dst, c, n); }
-
 static size_t strlen(const char *s) {
   size_t n = 0;
   while (s[n])
diff --git a/src/clayterm.c b/src/clayterm.c
index 1047062..52481a5 100644
--- a/src/clayterm.c
+++ b/src/clayterm.c
@@ -13,6 +13,7 @@
 #include "../clay/clay.h"
 #include "buffer.h"
 #include "cell.h"
+#include "mem.h"
 #include "utf8.h"
 #include "wcwidth.h"
 
@@ -290,7 +291,7 @@ static uint32_t rd(uint32_t *buf, int len, int *i) {
 static float rdf(uint32_t *buf, int len, int *i) {
   uint32_t v = rd(buf, len, i);
   float f;
-  __builtin_memcpy(&f, &v, 4);
+  memcpy(&f, &v, 4);
   return f;
 }
 
diff --git a/src/mem.c b/src/mem.c
new file mode 100644
index 0000000..77818fd
--- /dev/null
+++ b/src/mem.c
@@ -0,0 +1,18 @@
+/* mem.c — memcpy/memset shims for freestanding wasm32 */
+
+#include "mem.h"
+
+void *memcpy(void *dst, const void *src, size_t n) {
+  unsigned char *d = (unsigned char *)dst;
+  const unsigned char *s = (const unsigned char *)src;
+  while (n--)
+    *d++ = *s++;
+  return dst;
+}
+
+void *memset(void *dst, int c, size_t n) {
+  unsigned char *d = (unsigned char *)dst;
+  while (n--)
+    *d++ = (unsigned char)c;
+  return dst;
+}
diff --git a/src/mem.h b/src/mem.h
new file mode 100644
index 0000000..747b921
--- /dev/null
+++ b/src/mem.h
@@ -0,0 +1,11 @@
+/* mem.h — memcpy/memset shims for freestanding wasm32 */
+
+#ifndef MEM_H
+#define MEM_H
+
+typedef __SIZE_TYPE__ size_t;
+
+void *memcpy(void *dst, const void *src, size_t n);
+void *memset(void *dst, int c, size_t n);
+
+#endif
diff --git a/src/module.c b/src/module.c
index 398535b..75276c0 100644
--- a/src/module.c
+++ b/src/module.c
@@ -2,8 +2,9 @@
 
 #include "../clay/clay.h"
 
+#include "mem.c"
 #include "buffer.c"
 #include "cell.c"
-#include "clayterm.c"
 #include "utf8.c"
 #include "wcwidth.c"
+#include "clayterm.c"