diff --git a/artiq/language/scan.py b/artiq/language/scan.py
index fc20d98fc..522321a16 100644
--- a/artiq/language/scan.py
+++ b/artiq/language/scan.py
@@ -1,4 +1,6 @@
-from random import Random
+from random import Random, shuffle
+
+from artiq.language.core import *
 
 
 class LinearScan:
@@ -7,28 +9,32 @@ class LinearScan:
         self.max = max
         self.npoints = npoints
 
+    @portable
     def _gen(self):
         r = self.max - self.min
         d = self.npoints - 1
         for i in range(self.npoints):
             yield r*i/d + self.min
 
+    @portable
     def __iter__(self):
         return self._gen()
 
 
 class RandomScan:
     def __init__(self, min, max, npoints, seed=0):
-        self.min = min
-        self.max = max
-        self.npoints = npoints
-        self.seed = 0
-    
-    def _gen(self):
-        prng = Random(self.seed)
-        r = self.max - self.min
-        for i in range(self.npoints):
-            yield prng.random()*r + self.min
+        self.sequence = list(LinearScan(min, max, npoints))
+        shuffle(self.sequence, Random(seed).random)
 
+    @portable
     def __iter__(self):
-        return self._gen()
+        return iter(self.sequence)
+
+
+class ExplicitScan:
+    def __init__(self, sequence):
+        self.sequence = sequence
+
+    @portable
+    def __iter__(self):
+        return iter(self.sequence)