diff --git a/third-party/mimalloc/src/prim/unix/prim.c b/third-party/mimalloc/src/prim/unix/prim.c
index 8d4053631e..7e4e8f7bc4 100644
--- a/third-party/mimalloc/src/prim/unix/prim.c
+++ b/third-party/mimalloc/src/prim/unix/prim.c
@@ -28,6 +28,7 @@ terms of the MIT license. A copy of the license can be found in the file
 #include <sys/mman.h>  // mmap
 #include <unistd.h>    // sysconf
 #include <fcntl.h>     // open, close, read, access
+#include <stdlib.h>
   
 #if defined(__linux__)
   #include <features.h>