diff --git a/src/scheme/proc.rs b/src/scheme/proc.rs
index 4216c6782a..dd9adbb528 100644
--- a/src/scheme/proc.rs
+++ b/src/scheme/proc.rs
@@ -1316,15 +1316,25 @@ impl ContextHandle {
                     op @ ADDRSPACE_OP_MMAP | op @ ADDRSPACE_OP_TRANSFER => {
                         let fd = next()??;
                         let offset = next()??;
-                        let page_span = crate::syscall::validate_region(next()??, next()??)?;
-                        let flags = MapFlags::from_bits(next()??).ok_or(Error::new(EINVAL))?;
+                        let addr_raw = next()??;
+                        let size_raw = next()??;
+                        let flags_raw = next()??;
+                        info!("AS:MMAP fd={} off={} addr={:#x} size={:#x} flags={:#x}", fd, offset, addr_raw, size_raw, flags_raw);
+                        let page_span = crate::syscall::validate_region(addr_raw, size_raw)?;
+                        let flags = match MapFlags::from_bits(flags_raw) {
+                            Some(f) => f,
+                            None => {
+                                info!("AS:MMAP MapFlags::from_bits FAILED");
+                                return Err(Error::new(EINVAL));
+                            }
+                        };
 
                         if fd == !0 {
                             if op == ADDRSPACE_OP_TRANSFER {
                                 return Err(Error::new(EOPNOTSUPP));
                             }
 
-                            return MemoryScheme::fmap_anonymous(
+                            let res = MemoryScheme::fmap_anonymous(
                                 &addrspace,
                                 &Map {
                                     offset,
@@ -1335,6 +1345,11 @@ impl ContextHandle {
                                 false,
                                 token,
                             );
+                            match res {
+                                Ok(a) => { info!("AS:MMAP fmap_anonymous ok addr={:#x}", a); }
+                                Err(ref e) => { info!("AS:MMAP fmap_anonymous ERR errno={}", e.errno); }
+                            };
+                            return res;
                         } else {
                             let (scheme, number) = extract_scheme_number(fd, token)?;