diff --git a/basis/compiler/cfg/instructions/instructions.factor b/basis/compiler/cfg/instructions/instructions.factor
index 8e668c8f11..de18a9b5f9 100644
--- a/basis/compiler/cfg/instructions/instructions.factor
+++ b/basis/compiler/cfg/instructions/instructions.factor
@@ -303,11 +303,13 @@ literal: rep ;
 PURE-INSN: ##unpack-vector-head
 def: dst
 use: src
+temp: temp
 literal: rep ;
 
 PURE-INSN: ##unpack-vector-tail
 def: dst
 use: src
+temp: temp
 literal: rep ;
 
 PURE-INSN: ##integer>float-vector
@@ -813,8 +815,6 @@ UNION: def-is-use-insn
 ##box-displaced-alien
 ##compare-vector
 ##not-vector
-##unpack-vector-head
-##unpack-vector-tail
 ##string-nth
 ##unbox-any-c-ptr ;
 
diff --git a/basis/cpu/architecture/architecture.factor b/basis/cpu/architecture/architecture.factor
index 67f5018f58..b1417a590e 100644
--- a/basis/cpu/architecture/architecture.factor
+++ b/basis/cpu/architecture/architecture.factor
@@ -234,8 +234,8 @@ HOOK: %merge-vector-head cpu ( dst src1 src2 rep -- )
 HOOK: %merge-vector-tail cpu ( dst src1 src2 rep -- )
 HOOK: %signed-pack-vector cpu ( dst src1 src2 rep -- )
 HOOK: %unsigned-pack-vector cpu ( dst src1 src2 rep -- )
-HOOK: %unpack-vector-head cpu ( dst src rep -- )
-HOOK: %unpack-vector-tail cpu ( dst src rep -- )
+HOOK: %unpack-vector-head cpu ( dst src temp rep -- )
+HOOK: %unpack-vector-tail cpu ( dst src temp rep -- )
 HOOK: %integer>float-vector cpu ( dst src rep -- )
 HOOK: %float>integer-vector cpu ( dst src rep -- )
 HOOK: %compare-vector cpu ( dst src1 src2 temp rep cc -- )
diff --git a/basis/cpu/x86/x86.factor b/basis/cpu/x86/x86.factor
index 4d3a3203a8..ef0ccf971e 100644
--- a/basis/cpu/x86/x86.factor
+++ b/basis/cpu/x86/x86.factor
@@ -783,23 +783,25 @@ M: x86 %unsigned-pack-vector-reps
         { longlong-2-rep [ PCMPGTQ ] }
     } case ;
 
-:: (%unpack-vector-dest) ( dst src rep -- )
+:: (%unpack-vector-signs) ( dst src rep -- )
     dst rep signed-int-vector-rep?
     [ src rep %sign-extension-vector ]
     [ rep %zero-vector ] if ;
 
-M: x86 %unpack-vector-head ( dst src rep -- )
-    [ (%unpack-vector-dest) ] 3keep
-    unsign-rep {
+M:: x86 %unpack-vector-head ( dst src temp rep -- )
+    temp src rep (%unpack-vector-signs)
+    dst src rep %copy
+    dst temp rep unsign-rep {
         { char-16-rep    [ PUNPCKLBW ] }
         { short-8-rep    [ PUNPCKLWD ] }
         { int-4-rep      [ PUNPCKLDQ ] }
         { longlong-2-rep [ PUNPCKLQDQ ] }
     } case ;
 
-M: x86 %unpack-vector-tail ( dst src rep -- )
-    [ (%unpack-vector-dest) ] 3keep
-    unsign-rep {
+M:: x86 %unpack-vector-tail ( dst src temp rep -- )
+    temp src rep (%unpack-vector-signs)
+    dst src rep %copy
+    dst temp rep unsign-rep {
         { char-16-rep    [ PUNPCKHBW ] }
         { short-8-rep    [ PUNPCKHWD ] }
         { int-4-rep      [ PUNPCKHDQ ] }