diff --git a/src/crab/cpu.cr b/src/crab/cpu.cr
index cec0b27..19e2491 100644
--- a/src/crab/cpu.cr
+++ b/src/crab/cpu.cr
@@ -103,7 +103,7 @@ class CPU
   # Arithmetic shift right
   def asr(word : Word, bits : Int, set_conditions : Bool) : Word
     log "asr - word:#{hex_str word}, bits:#{bits}"
-    bits = 32 if bits == 0
+    return word if bits == 0
     @cpsr.carry = bit?(word, bits - 1) if set_conditions
     word >> bits | (0xFFFFFFFF_u32 &* (word >> 31)) << (32 - bits)
   end