The value NIL is not of type NUMBER in compiling lambda with case form, dead code

[Paul F. Dietz]

(lambda (b)
  (declare (type (integer 605 829) b))
  (case b ((2) b) ((-3 3 -4) 0) (t 0)))

==>

The value
  NIL
is not of type
  NUMBER
   [Condition of type TYPE-ERROR]

Restarts:
 0: [RETRY] Retry SLIME REPL evaluation request.
 1: [*ABORT] Return to SLIME's top level.
 2: [ABORT] abort thread (#<THREAD tid=32557 "repl-thread" RUNNING {1001908003}>)

Backtrace:
  0: (SB-KERNEL:TWO-ARG-+ 49 NIL)
  1: ((LAMBDA (SB-ASSEM:SEGMENT SB-ASSEM::POSN) :IN "SYS:SRC;COMPILER;ASSEM.LISP") #<SB-ASSEM:SEGMENT {1006B7CDE3}> #<unused argument>)
  2: (SB-ASSEM::PROCESS-BACK-PATCHES #<SB-ASSEM:SEGMENT {1006B7CDE3}>)
  3: (SB-ASSEM:FINALIZE-SEGMENT #<SB-ASSEM:SEGMENT {1006B7CDE3}>)
  4: (SB-ASSEM:ASSEMBLE-SECTIONS #S(SB-ASSEM::ASMSTREAM :DATA-SECTION (#<SB-ASSEM::STMT IGNORE {1006B7BBB3}> . #<SB-ASSEM::STMT .ALIGN {1006B7CF23}>) :CODE-SECTION (#1=#<SB-ASSEM::STMT IGNORE {1006B7BBF3}>..
  5: (SB-C::GENERATE-CODE #<SB-C:COMPONENT :NAME "<unknown>" {1006B36AD3}>)
  6: (SB-C::%COMPILE-COMPONENT #<SB-C:COMPONENT :NAME "<unknown>" {1006B36AD3}>)
[...]

x86-64, "2.4.2.192-0548f3209"