diff --git a/miasm/arch/aarch64/arch.py b/miasm/arch/aarch64/arch.py
index c642d2010..5246d9201 100644
--- a/miasm/arch/aarch64/arch.py
+++ b/miasm/arch/aarch64/arch.py
@@ -1424,7 +1424,7 @@ def decode(self, v):
     def encode(self):
         v = int(self.expr)
         if v & (1 << 63):
-            v &= (1 << 33) - 1
+            v &= (1 << 21) - 1
         self.parent.immlo.value = v & 3
         v >>= 2
         if v > (1 << 19) - 1:
diff --git a/test/arch/aarch64/arch.py b/test/arch/aarch64/arch.py
index 4156e054c..7d81e45e0 100644
--- a/test/arch/aarch64/arch.py
+++ b/test/arch/aarch64/arch.py
@@ -1846,7 +1846,10 @@
     ("XXXXXXXX    TLBI       0x0, c7, 0x0, XZR",
      "1F8708D5"),
     ("XXXXXXXX    YIELD      ",
-     "3F2003D5")
+     "3F2003D5"),
+
+    ("XXXXXXXX    ADR        X29, 0xFFFFFFFFFFFFFAC8",
+     "5DD6FF10"),
 ]