diff --git a/decode.c b/decode.c
index a8a8df7..9aa2cdb 100644
--- a/decode.c
+++ b/decode.c
@@ -24,7 +24,8 @@ static uint64_t immlogical(unsigned sf, unsigned N, unsigned immr,
   unsigned esize = 1 << len;
   uint64_t welem = ((uint64_t)1 << (s + 1)) - 1;
   // ROR(welem, r) as bits(esize)
-  welem = (welem >> r) | (welem << (esize - r));
+  if (r)
+    welem = (welem >> r) | (welem << (esize - r));
   if (esize < 64)
     welem &= ((uint64_t)1 << esize) - 1;
   // Replicate(ROR(welem, r))
diff --git a/parse.py b/parse.py
index 4918522..51ea0cc 100644
--- a/parse.py
+++ b/parse.py
@@ -548,10 +548,10 @@ def add_mnem(self, grp: str, name: str, grpdesc: Desc, descmask: MaskedVal, ops:
         # use XOR s.t. immadd can toggle between add and sub.
         buildexprs = ["(" + "^".join([f"{descmask.val:#x}"] + grandExpansions) + ")"]
         for de in grpdesc:
-            bitmask = ((1 << de.size) - 1) << de.idx
+            bitmask = (1 << de.size) - 1
             if de.name in assignments:
-                buildexprs.append(f"(({assignments[de.name]})<<{de.idx}&{bitmask:#x})")
-            elif descmask.mask & bitmask != bitmask:
+                buildexprs.append(f"((({assignments[de.name]})&{bitmask:#x})<<{de.idx})")
+            elif descmask.mask & (bitmask << de.idx) != (bitmask << de.idx):
                 print("Encode desc missing for", grp, name, de.name, assignments)
                 return
         expr = "|".join(buildexprs)