diff --git a/extra/cpu/8080/emulator/emulator.factor b/extra/cpu/8080/emulator/emulator.factor
index 4e166a646d..f79a70c50f 100644
--- a/extra/cpu/8080/emulator/emulator.factor
+++ b/extra/cpu/8080/emulator/emulator.factor
@@ -499,13 +499,15 @@ SYMBOL: rom-root
   [ over 1 + swap pc<< ] keep
   read-byte ;
 
+ERROR: undefined-8080-opcode n ;
+
 : get-cycles ( n -- opcode )
   #! Returns the cycles for the given instruction value.
   #! If the opcode is not defined throw an error.
   dup instruction-cycles nth [ 
     nip  
   ] [
-    [ "Undefined 8080 opcode: " % number>string % ] "" make throw
+    undefined-8080-opcode
   ] if* ;
 
 : process-interrupts ( cpu -- )