diff --git a/src/syscall/process.rs b/src/syscall/process.rs
index 307a266..e051197 100644
--- a/src/syscall/process.rs
+++ b/src/syscall/process.rs
@@ -455,11 +455,15 @@ pub fn clone(flags: CloneFlags, stack_base: usize) -> Result<ContextId> {
 
                 // Copy user heap mapping, if found
                 if let Some(heap_shared) = heap_opt {
-                    let frame = active_table.p4()[crate::USER_HEAP_PML4].pointed_frame().expect("user heap not mapped");
-                    let flags = active_table.p4()[crate::USER_HEAP_PML4].flags();
-                    active_table.with(&mut new_table, &mut temporary_page, |mapper| {
-                        mapper.p4_mut()[crate::USER_HEAP_PML4].set(frame, flags);
-                    });
+                    //TODO: find out why this gets unmapped (perhaps it is never mapped)
+                    if let Some(frame) = active_table.p4()[crate::USER_HEAP_PML4].pointed_frame() {
+                        let flags = active_table.p4()[crate::USER_HEAP_PML4].flags();
+                        active_table.with(&mut new_table, &mut temporary_page, |mapper| {
+                            mapper.p4_mut()[crate::USER_HEAP_PML4].set(frame, flags);
+                        });
+                    } else {
+                        println!("clone: user heap not mapped for {:X?}", heap_shared);
+                    }
                     context.heap = Some(heap_shared);
                 }