diff --git a/bin/build.sh b/bin/build.sh
index ed726d3826e8fe1e0a4bdca3d95e952073668f95..211007a42944426aa038fb101f189616e021c9a2 100755
--- a/bin/build.sh
+++ b/bin/build.sh
@@ -39,7 +39,7 @@ ENABLE2="yes"
 ENABLE3="yes"
 ENABLE4="yes"
 
-version=21a
+version=21b
 SRCDIR=src
 BINDIR=bin
 TOOLDIR=$BINDIR
diff --git a/src/bootfiles/21b/boot-2017-01-1.lisp b/src/bootfiles/21b/boot-2017-01-1.lisp
new file mode 100644
index 0000000000000000000000000000000000000000..845efe2b716c92fcd112ddbaed9fa6c9e2f30d57
--- /dev/null
+++ b/src/bootfiles/21b/boot-2017-01-1.lisp
@@ -0,0 +1,132 @@
+;; Boot file to increase the max alignment value from 3 to 4.
+;;
+;; This takes care of everything for the bootstrap, but when new-assem
+;; is loaded. you'll get a warning.  Select the CLOBBER-IT restart to
+;; continue.
+
+(in-package :new-assem)
+
+(handler-bind
+    ((error (lambda (c)
+	      (declare (ignore c))
+	      (invoke-restart 'continue))))
+  (defconstant max-alignment 4))
+
+(ext:without-package-locks
+(deftype alignment ()
+  `(integer 0 ,max-alignment))
+)
+
+(ext:without-package-locks
+(handler-bind ((error (lambda (c)
+			(declare (ignore c))
+			(invoke-restart 'kernel::clobber-it))))
+  (defstruct (segment
+	      (:print-function %print-segment)
+	      (:constructor make-segment (&key name run-scheduler inst-hook)))
+    ;;
+    ;; The name of this segment.  Only using in trace files.
+    (name "Unnamed" :type simple-base-string)
+    ;;
+    ;; Whether or not run the scheduler.  Note: if the instruction defintions
+    ;; were not compiled with the scheduler turned on, this has no effect.
+    (run-scheduler nil)
+    ;;
+    ;; If a function, then it is funcalled for each inst emitted with the
+    ;; segment, the VOP, the name of the inst (as a string), and the inst
+    ;; arguments.
+    (inst-hook nil :type (or function null))
+    ;;
+    ;; Where to deposit the next byte.
+    (fill-pointer (system:int-sap 0) :type system:system-area-pointer)
+    ;;
+    ;; Where the current output block ends.  If fill-pointer is ever sap= to
+    ;; this, don't deposit a byte.  Move the fill pointer into a new block.
+    (block-end (system:int-sap 0) :type system:system-area-pointer)
+    ;;
+    ;; What position does this correspond to.  Initially, positions and indexes
+    ;; are the same, but after we start collapsing choosers, positions can change
+    ;; while indexes stay the same.
+    (current-posn 0 :type posn)
+    ;;
+    ;; Were in the output blocks are we currently outputing.
+    (current-index 0 :type index)
+    ;;
+    ;; A vector of the output blocks.
+    (output-blocks (make-array 4 :initial-element nil) :type simple-vector)
+    ;;
+    ;; A list of all the annotations that have been output to this segment.
+    (annotations nil :type list)
+    ;;
+    ;; A pointer to the last cons cell in the annotations list.  This is
+    ;; so we can quickly add things to the end of the annotations list.
+    (last-annotation nil :type list)
+    ;;
+    ;; The number of bits of alignment at the last time we synchronized.
+    (alignment max-alignment :type alignment)
+    ;;
+    ;; The position the last time we synchronized.
+    (sync-posn 0 :type posn)
+    ;;
+    ;; The posn and index everything ends at.  This is not maintained while the
+    ;; data is being generated, but is filled in after.  Basically, we copy
+    ;; current-posn and current-index so that we can trash them while processing
+    ;; choosers and back-patches.
+    (final-posn 0 :type posn)
+    (final-index 0 :type index)
+    ;;
+    ;; *** State used by the scheduler during instruction queueing.
+    ;;
+    ;; List of postit's.  These are accumulated between instructions.
+    (postits nil :type list)
+    ;;
+    ;; ``Number'' for last instruction queued.  Used only to supply insts
+    ;; with unique sset-element-number's.
+    (inst-number 0 :type index)
+    ;;
+    ;; Simple-Vectors mapping locations to the instruction that reads them and
+    ;; instructions that write them.
+    (readers (make-array (assem-params-max-locations
+			  (c:backend-assembler-params c:*backend*))
+			 :initial-element nil)
+     :type simple-vector)
+    (writers (make-array (assem-params-max-locations
+			  (c:backend-assembler-params c:*backend*))
+			 :initial-element nil)
+     :type simple-vector)
+    ;;
+    ;; The number of additional cycles before the next control transfer, or NIL
+    ;; if a control transfer hasn't been queued.  When a delayed branch is
+    ;; queued, this slot is set to the delay count.
+    (branch-countdown nil :type (or null (and fixnum unsigned-byte)))
+    ;;
+    ;; *** These two slots are used both by the queuing noise and the
+    ;; scheduling noise.
+    ;;
+    ;; All the instructions that are pending and don't have any unresolved
+    ;; dependents.  We don't list branches here even if they would otherwise
+    ;; qualify.  They are listed above.
+    ;;
+    (emittable-insts-sset (make-sset) :type sset)
+    ;;
+    ;; List of queued branches.  We handle these specially, because they have to
+    ;; be emitted at a specific place (e.g. one slot before the end of the
+    ;; block).
+    (queued-branches nil :type list)
+    ;;
+    ;; *** State used by the scheduler duing instruction scheduling.
+    ;;
+    ;; The instructions who would have had a read dependent removed if it were
+    ;; not for a delay slot.  This is a list of lists.  Each element in the
+    ;; top level list corresponds to yet another cycle of delay.  Each element
+    ;; in the second level lists is a dotted pair, holding the dependency
+    ;; instruction and the dependent to remove.
+    (delayed nil :type list)
+    ;;
+    ;; The emittable insts again, except this time as a list sorted by depth.
+    (emittable-insts-queue nil :type list)
+    ;;
+    ;; Whether or not to collect dynamic statistics.  This is just the same as
+    ;; *collect-dynamic-statistics* but is faster to reference.
+    (collect-dynamic-statistics nil))))
+
diff --git a/src/compiler/new-assem.lisp b/src/compiler/new-assem.lisp
index f6179dea4e815a494807f063d07932695fcdae9e..54059c67d34caf071cd06337c51b1917d8421e27 100644
--- a/src/compiler/new-assem.lisp
+++ b/src/compiler/new-assem.lisp
@@ -80,7 +80,7 @@
 ;;; format.  If the loader only loads objects 8-byte aligned, we can't do
 ;;; any better than that ourselves.
 ;;;
-(defconstant max-alignment 3)
+(defconstant max-alignment 4)
 
 (deftype alignment ()
   `(integer 0 ,max-alignment))