diff --git a/artiq/firmware/ksupport/api.rs b/artiq/firmware/ksupport/api.rs
index 3e99731b4..1682f818b 100644
--- a/artiq/firmware/ksupport/api.rs
+++ b/artiq/firmware/ksupport/api.rs
@@ -63,7 +63,10 @@ static mut API: &'static [(&'static str, *const ())] = &[
     api!(__powidf2),
 
     /* libc */
-    api!(memcmp, extern { fn memcmp(a: *const u8, b: *mut u8, size: usize); }),
+    api!(memcpy, extern { fn memcpy(dest: *mut u8, src: *const u8, n: usize) -> *mut u8; }),
+    api!(memmove, extern { fn memmove(dest: *mut u8, src: *const u8, n: usize) -> *mut u8; }),
+    api!(memset, extern { fn memset(s: *mut u8, c: i32, n: usize) -> *mut u8; }),
+    api!(memcmp, extern { fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32; }),
 
     /* libm */
     // commented out functions are not available with the libm used here, but are available in NAR3.