read from string stream does not ignore errors

[daly]

(setq a ")abbrev")
(setq b (make-string-input-stream a))
(read b nil :eof) ; fails -- should not throw error

in SBCL 1.4.6 on Ubuntu

uname -a
Linux COQ16 4.4.0-93-generic #116-Ubuntu SMP Fri Aug 11 21:17:51 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

*features*
(:64-BIT :64-BIT-REGISTERS :ALIEN-CALLBACKS :ANSI-CL :ASH-RIGHT-VOPS
 :C-STACK-IS-CONTROL-STACK :CALL-SYMBOL :COMMON-LISP :COMPACT-INSTANCE-HEADER
 :COMPARE-AND-SWAP-VOPS :COMPLEX-FLOAT-VOPS :CYCLE-COUNTER :ELF :FLOAT-EQL-VOPS
 :FP-AND-PC-STANDARD-SAVE :GCC-TLS :GENCGC :IEEE-FLOATING-POINT :IMMOBILE-CODE
 :IMMOBILE-SPACE :INLINE-CONSTANTS :INTEGER-EQL-VOP :LARGEFILE :LINKAGE-TABLE
 :LINUX :LITTLE-ENDIAN :MEMORY-BARRIER-VOPS :MULTIPLY-HIGH-VOPS
 :OS-PROVIDES-DLADDR :OS-PROVIDES-DLOPEN :OS-PROVIDES-GETPROTOBY-R
 :OS-PROVIDES-POLL :OS-PROVIDES-PUTWC :OS-PROVIDES-SUSECONDS-T
 :PACKAGE-LOCAL-NICKNAMES :RAW-INSTANCE-INIT-VOPS :RAW-SIGNED-WORD
 :RELOCATABLE-HEAP :SB-DOC :SB-EVAL :SB-FUTEX :SB-LDB :SB-PACKAGE-LOCKS
 :SB-SIMD-PACK :SB-SOURCE-LOCATIONS :SB-THREAD :SB-UNICODE :SBCL
 :STACK-ALLOCATABLE-CLOSURES :STACK-ALLOCATABLE-FIXED-OBJECTS
 :STACK-ALLOCATABLE-LISTS :STACK-ALLOCATABLE-VECTORS
 :STACK-GROWS-DOWNWARD-NOT-UPWARD :SYMBOL-INFO-VOPS :UNBIND-N-VOP
 :UNDEFINED-FUN-RESTARTS :UNIX :UNWIND-TO-FRAME-AND-CALL-VOP :X86-64)

[Stas Boukarev (stassats)]

Wait, why should it not produce an error?