diff --git a/lslopt/lslbasefuncs.py b/lslopt/lslbasefuncs.py
index a150545..0239490 100644
--- a/lslopt/lslbasefuncs.py
+++ b/lslopt/lslbasefuncs.py
@@ -1663,19 +1663,24 @@ def llListReplaceList(lst, elems, start, end):
     if end == -1: end += L
     return lst[:start] + elems + lst[end+1:]
 
-def llListSort(lst, stride, asc):
+def llListSort(lst, stride, asc, idx=0):
     lst = fl(lst)
     stride = fi(stride)
     asc = fi(asc)
     lst = lst[:]  # make a copy
     L = len(lst)
     broken = u'\ufb1a' > u'\U0001d41a'  # that happens on Windows
-    if stride < 1: stride = 1
+    if stride < 1:
+        stride = 1
     if L % stride:
         return lst
+    if idx < 0:
+        idx += stride
+    if not (0 <= idx < stride):
+        return []
     for i in xrange(0, L-stride, stride):
         # Optimized by caching the element in the outer loop AND after swapping.
-        a = lst[i]
+        a = lst[i+idx]
         ta = type(a)
         if ta == Vector:
             a = v2f(a)  # list should contain vectors made only of floats
@@ -1688,7 +1693,7 @@ def llListSort(lst, stride, asc):
             # It should be OK because only equal types are compared.
             a = a.encode('utf-32-be')  # pragma: no cover
         for j in xrange(i+stride, L, stride):
-            b = lst[j]
+            b = lst[j+idx]
             tb = type(b)
             gt = False
             if ta == tb:
@@ -1717,11 +1722,8 @@ def llListSort(lst, stride, asc):
     return lst
 
 def llListSortStrided(src, stride, idx, ascending):
-    src = fl(src)
-    stride = fi(stride)
     idx = fi(idx)
-    ascending = fi(ascending)
-    raise ELSLCantCompute  # TODO: Implement llListSortStrided
+    return llListSort(src, stride, ascending, idx)
 
 def llListStatistics(op, lst):
     op = fi(op)
diff --git a/unit_tests/expr.suite/list-funcs-7.lsl b/unit_tests/expr.suite/list-funcs-7.lsl
new file mode 100644
index 0000000..fff867d
--- /dev/null
+++ b/unit_tests/expr.suite/list-funcs-7.lsl
@@ -0,0 +1,9 @@
+  "T1" + llListSortStrided(["a", "á", "B", "C", "d", "e"], 1, 0, TRUE)
++ "T2" + llListSortStrided([1, "C", 3, "A", 2, "B"], 1, 0, TRUE)
++ "T3" + llListSortStrided([1, 3, 2, "C", "A", "B"], 1, 0, TRUE)
++ "T4" + llListSortStrided([1, "C", 3, "A", 2, "B"], 2, 0, TRUE)
++ "T5" + llListSortStrided([1, "C", 3, "A", 2, "B"], 2, 1, TRUE)
++ "T6" + llListSortStrided([1, "C", 3, "A", 2, "B"], 2, 2, TRUE)
++ "T7" + llListSortStrided([1, "C", 3, "A", 2, "B"], 2, -3, TRUE)
++ "T8" + llListSortStrided([1, "C", 3, "A", 2, "B"], 2, -2, TRUE)
++ "T9" + llListSortStrided([1, "C", 3, "A", 2, "B"], 2, -1, TRUE)
diff --git a/unit_tests/expr.suite/list-funcs-7.out b/unit_tests/expr.suite/list-funcs-7.out
new file mode 100644
index 0000000..5d2a8fb
--- /dev/null
+++ b/unit_tests/expr.suite/list-funcs-7.out
@@ -0,0 +1,52 @@
+[ "T1"
+, "B"
+, "C"
+, "a"
+, "d"
+, "e"
+, "á"
+, "T2"
+, 1
+, "A"
+, 2
+, "B"
+, 3
+, "C"
+, "T3"
+, 1
+, 2
+, 3
+, "A"
+, "B"
+, "C"
+, "T4"
+, 1
+, "C"
+, 2
+, "B"
+, 3
+, "A"
+, "T5"
+, 3
+, "A"
+, 2
+, "B"
+, 1
+, "C"
+, "T6"
+, "T7"
+, "T8"
+, 1
+, "C"
+, 2
+, "B"
+, 3
+, "A"
+, "T9"
+, 3
+, "A"
+, 2
+, "B"
+, 1
+, "C"
+]
\ No newline at end of file