diff --git a/lang/cem/libcc.ansi/build.lua b/lang/cem/libcc.ansi/build.lua
index 18b2a44d6..38fba6bb3 100644
--- a/lang/cem/libcc.ansi/build.lua
+++ b/lang/cem/libcc.ansi/build.lua
@@ -43,8 +43,7 @@ for _, plat in ipairs(vars.plats) do
 			"./core/math/*.e",
 			"./core/ctype/*.c",
 			"./core/misc/*.c",
-			"./errno/*.c",
-			"./malloc/*.c",
+			"./sys/malloc/*.c",
 			"./signal/*.c",
 			"./assert/*.c",
 			"./stdio/*.c",
@@ -58,7 +57,7 @@ for _, plat in ipairs(vars.plats) do
 		deps = {
 			"lang/cem/libcc.ansi/headers+pkg",
 			"plat/"..plat.."/include+pkg",
-			"./malloc/malloc.h",
+			"./sys/malloc/malloc.h",
 			"./core/math/localmath.h",
 			"./core/stdlib/ext_fmt.h",
 			"./stdio/loc_incl.h",
diff --git a/lang/cem/libcc.ansi/sys/README.md b/lang/cem/libcc.ansi/sys/README.md
new file mode 100644
index 000000000..b38a2f08f
--- /dev/null
+++ b/lang/cem/libcc.ansi/sys/README.md
@@ -0,0 +1,4 @@
+The functions here all use Posix system calls to do the actual work, and so
+require `unistd.h` (at the minimum). Typically each group of functions will
+be protected by an `ACKCONF` variable so the plat can turn them on and off as
+necessary.
diff --git a/lang/cem/libcc.ansi/malloc/calloc.c b/lang/cem/libcc.ansi/sys/malloc/calloc.c
similarity index 93%
rename from lang/cem/libcc.ansi/malloc/calloc.c
rename to lang/cem/libcc.ansi/sys/malloc/calloc.c
index 8695f17f0..e21c5266a 100644
--- a/lang/cem/libcc.ansi/malloc/calloc.c
+++ b/lang/cem/libcc.ansi/sys/malloc/calloc.c
@@ -3,6 +3,8 @@
 #include <unistd.h>
 #include <string.h>
 
+#if ACKCONF_WANT_MALLOC
+
 void* calloc(size_t nmemb, size_t size)
 {
 	size_t bytes = nmemb * size;
@@ -22,3 +24,5 @@ void* calloc(size_t nmemb, size_t size)
 	memset(ptr, 0, bytes);
 	return ptr;
 }
+
+#endif
diff --git a/lang/cem/libcc.ansi/malloc/malloc.c b/lang/cem/libcc.ansi/sys/malloc/malloc.c
similarity index 98%
rename from lang/cem/libcc.ansi/malloc/malloc.c
rename to lang/cem/libcc.ansi/sys/malloc/malloc.c
index 71f3c80b2..ea1381600 100644
--- a/lang/cem/libcc.ansi/malloc/malloc.c
+++ b/lang/cem/libcc.ansi/sys/malloc/malloc.c
@@ -3,6 +3,8 @@
 #include <unistd.h>
 #include "malloc.h"
 
+#if ACKCONF_WANT_MALLOC
+
 block_t __mem_root = { &__mem_root, 0 };
 block_t* __mem_freelist = &__mem_root;
 
@@ -148,3 +150,5 @@ void free(void* ptr)
 	/* ...and update the ring pointer. */
 	__mem_freelist = p;
 }
+
+#endif
diff --git a/lang/cem/libcc.ansi/malloc/malloc.h b/lang/cem/libcc.ansi/sys/malloc/malloc.h
similarity index 100%
rename from lang/cem/libcc.ansi/malloc/malloc.h
rename to lang/cem/libcc.ansi/sys/malloc/malloc.h
diff --git a/lang/cem/libcc.ansi/malloc/realloc.c b/lang/cem/libcc.ansi/sys/malloc/realloc.c
similarity index 95%
rename from lang/cem/libcc.ansi/malloc/realloc.c
rename to lang/cem/libcc.ansi/sys/malloc/realloc.c
index c941d8091..6e2b4c924 100644
--- a/lang/cem/libcc.ansi/malloc/realloc.c
+++ b/lang/cem/libcc.ansi/sys/malloc/realloc.c
@@ -4,6 +4,8 @@
 #include <string.h>
 #include "malloc.h"
 
+#if ACKCONF_WANT_MALLOC
+
 void* realloc(void* ptr, size_t size)
 {
 	block_t* h;
@@ -39,3 +41,5 @@ void* realloc(void* ptr, size_t size)
 	free(ptr);
 	return newptr;
 }
+
+#endif