diff --git a/src/arch/isa_parser/isa_parser.py b/src/arch/isa_parser/isa_parser.py
index 39f884c..6a81fbe 100755
--- a/src/arch/isa_parser/isa_parser.py
+++ b/src/arch/isa_parser/isa_parser.py
@@ -1488,7 +1488,7 @@
         extensions = self.operandTypeMap.keys()
 
         operandsREString = r'''
-        (?<!\w)      # neg. lookbehind assertion: prevent partial matches
+        (?<!\w|:)     # neg. lookbehind assertion: prevent partial matches
         ((%s)(?:_(%s))?)   # match: operand with optional '_' then suffix
         (?!\w)       # neg. lookahead assertion: prevent partial matches
         ''' % ('|'.join(operands), '|'.join(extensions))