diff --git a/basis/compiler/cfg/linear-scan/assignment/assignment.factor b/basis/compiler/cfg/linear-scan/assignment/assignment.factor
index ea717f9218..ab03882757 100644
--- a/basis/compiler/cfg/linear-scan/assignment/assignment.factor
+++ b/basis/compiler/cfg/linear-scan/assignment/assignment.factor
@@ -50,9 +50,12 @@ ERROR: already-spilled ;
 : handle-spill ( live-interval -- )
     dup spill-to>> [ [ record-spill ] [ insert-spill ] bi ] [ drop ] if ;
 
+: next-interval ( live-interval -- live-interval' )
+    split-next>> dup split-before>> [ next-interval ] [ ] ?if ;
+
 : insert-copy ( live-interval -- )
     {
-        [ split-next>> reg>> ]
+        [ next-interval reg>> ]
         [ reg>> ]
         [ vreg>> reg-class>> ]
         [ end>> ]
diff --git a/basis/math/vectors/vectors-tests.factor b/basis/math/vectors/vectors-tests.factor
index 968af6a3aa..3e56644d3e 100644
--- a/basis/math/vectors/vectors-tests.factor
+++ b/basis/math/vectors/vectors-tests.factor
@@ -16,3 +16,5 @@ USING: math.vectors tools.test ;
 [ { 1.75 2.125 } ] [ { 1.0 2.5 } { 2.5 1.0 } { 0.5 0.25 } vlerp ] unit-test 
 
 [ 1.125 ] [ 0.0 1.0 2.0 4.0 { 0.5 0.25 } bilerp ] unit-test
+
+[ 17 ] [ 0 1 2 3 4 5 6 7 { 1 2 3 } trilerp ] unit-test
\ No newline at end of file