diff --git a/git-compat-util.h b/git-compat-util.h
index 58d7708296..79977caed6 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -995,6 +995,28 @@ static inline unsigned long cast_size_t_to_ulong(size_t a)
 	return (unsigned long)a;
 }
 
+/*
+ * Limit size of IO chunks, because huge chunks only cause pain.  OS X
+ * 64-bit is buggy, returning EINVAL if len >= INT_MAX; and even in
+ * the absence of bugs, large chunks can result in bad latencies when
+ * you decide to kill the process.
+ *
+ * We pick 8 MiB as our default, but if the platform defines SSIZE_MAX
+ * that is smaller than that, clip it to SSIZE_MAX, as a call to
+ * read(2) or write(2) larger than that is allowed to fail.  As the last
+ * resort, we allow a port to pass via CFLAGS e.g. "-DMAX_IO_SIZE=value"
+ * to override this, if the definition of SSIZE_MAX given by the platform
+ * is broken.
+ */
+#ifndef MAX_IO_SIZE
+# define MAX_IO_SIZE_DEFAULT (8*1024*1024)
+# if defined(SSIZE_MAX) && (SSIZE_MAX < MAX_IO_SIZE_DEFAULT)
+#  define MAX_IO_SIZE SSIZE_MAX
+# else
+#  define MAX_IO_SIZE MAX_IO_SIZE_DEFAULT
+# endif
+#endif
+
 #ifdef HAVE_ALLOCA_H
 # include <alloca.h>
 # define xalloca(size)      (alloca(size))
diff --git a/wrapper.c b/wrapper.c
index 1c3c970080..f52f3e21cc 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -161,28 +161,6 @@ void xsetenv(const char *name, const char *value, int overwrite)
 		die_errno(_("could not setenv '%s'"), name ? name : "(null)");
 }
 
-/*
- * Limit size of IO chunks, because huge chunks only cause pain.  OS X
- * 64-bit is buggy, returning EINVAL if len >= INT_MAX; and even in
- * the absence of bugs, large chunks can result in bad latencies when
- * you decide to kill the process.
- *
- * We pick 8 MiB as our default, but if the platform defines SSIZE_MAX
- * that is smaller than that, clip it to SSIZE_MAX, as a call to
- * read(2) or write(2) larger than that is allowed to fail.  As the last
- * resort, we allow a port to pass via CFLAGS e.g. "-DMAX_IO_SIZE=value"
- * to override this, if the definition of SSIZE_MAX given by the platform
- * is broken.
- */
-#ifndef MAX_IO_SIZE
-# define MAX_IO_SIZE_DEFAULT (8*1024*1024)
-# if defined(SSIZE_MAX) && (SSIZE_MAX < MAX_IO_SIZE_DEFAULT)
-#  define MAX_IO_SIZE SSIZE_MAX
-# else
-#  define MAX_IO_SIZE MAX_IO_SIZE_DEFAULT
-# endif
-#endif
-
 /**
  * xopen() is the same as open(), but it die()s if the open() fails.
  */