diff --git a/osaca/parser/parser_AArch64.py b/osaca/parser/parser_AArch64.py
index 62ec851..85a8ad0 100644
--- a/osaca/parser/parser_AArch64.py
+++ b/osaca/parser/parser_AArch64.py
@@ -411,12 +411,12 @@ class ParserAArch64(BaseParser):
 
     def process_register_operand(self, operand):
         return RegisterOperand(
-            prefix=operand["prefix"],
+            prefix=operand["prefix"].lower(),
             name=operand["name"],
-            shape=operand["shape"] if "shape" in operand else None,
+            shape=operand["shape"].lower() if "shape" in operand else None,
             lanes=operand["lanes"] if "lanes" in operand else None,
             index=operand["index"] if "index" in operand else None,
-            predication=operand["predication"] if "predication" in operand else None,
+            predication=operand["predication"].lower() if "predication" in operand else None,
         )
 
     def process_memory_address(self, memory_address):
diff --git a/osaca/parser/parser_x86att.py b/osaca/parser/parser_x86att.py
index 85dfd0d..c5f0627 100644
--- a/osaca/parser/parser_x86att.py
+++ b/osaca/parser/parser_x86att.py
@@ -311,12 +311,12 @@ class ParserX86ATT(BaseParser):
 
     def process_register(self, operand):
         return RegisterOperand(
-            prefix=operand["prefix"] if "prefix" in operand else None,
+            prefix=operand["prefix"].lower() if "prefix" in operand else None,
             name=operand["name"],
-            shape=operand["shape"] if "shape" in operand else None,
+            shape=operand["shape"].lower() if "shape" in operand else None,
             lanes=operand["lanes"] if "lanes" in operand else None,
             index=operand["index"] if "index" in operand else None,
-            predication=operand["predication"] if "predication" in operand else None,
+            predication=operand["predication"].lower() if "predication" in operand else None,
         )
 
     def process_directive(self, directive):
diff --git a/osaca/parser/register.py b/osaca/parser/register.py
index 23d4778..e3effaf 100644
--- a/osaca/parser/register.py
+++ b/osaca/parser/register.py
@@ -26,14 +26,14 @@ class RegisterOperand(Operand):
         super().__init__(source, destination)
         self._name = name
         self._width = width
-        self._prefix = prefix
+        self._prefix = prefix.lower() if prefix else None
         self._regtype = regtype
         self._lanes = lanes
-        self._shape = shape
+        self._shape = shape.lower() if shape else None
         self._index = index
         self._mask = mask
         self._zeroing = zeroing
-        self._predication = predication
+        self._predication = predication.lower() if predication else None
         self._pre_indexed = pre_indexed
         self._post_indexed = post_indexed
         self._shift = shift
@@ -93,7 +93,7 @@ class RegisterOperand(Operand):
 
     @prefix.setter
     def prefix(self, prefix):
-        self._prefix = prefix
+        self._prefix = prefix.lower()
 
     @property
     def regtype(self):