diff --git a/redox-rt/src/proc.rs b/redox-rt/src/proc.rs
index de03a80b94..d24e66f9a8 100644
--- a/redox-rt/src/proc.rs
+++ b/redox-rt/src/proc.rs
@@ -740,7 +740,7 @@ impl<'a> MmapGuard<'a> {
                 size,
                 offset,
                 address: 0,
-                flags: PROT_READ | PROT_WRITE,
+                flags: PROT_READ | PROT_WRITE | MapFlags::MAP_SHARED,
             },
         )?;
         let slice = unsafe { &mut *this.as_mut_ptr_slice() };