diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index df6f2a9d0f..833f853200 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -839,7 +839,7 @@ void target_set_brk(abi_ulong new_brk)
 abi_long do_brk(abi_ulong new_brk)
 {
     abi_long mapped_addr;
-    int	new_alloc_size;
+    abi_ulong new_alloc_size;
 
     DEBUGF_BRK("do_brk(" TARGET_ABI_FMT_lx ") -> ", new_brk);