diff --git a/adaptive/runner.py b/adaptive/runner.py
index 9a8a9b1a5..2a47c7b75 100644
--- a/adaptive/runner.py
+++ b/adaptive/runner.py
@@ -54,6 +54,12 @@
 )
 
 
+def _key_by_value(dct, value):
+    for k, v in dct.items():
+        if v == value:
+            return k
+
+
 class BaseRunner(metaclass=abc.ABCMeta):
     r"""Base class for runners that use `concurrent.futures.Executors`.
 
@@ -146,11 +152,16 @@ def __init__(
         self.to_retry = {}
         self.tracebacks = {}
 
+        # Keeping track of index -> point
+        self.index_to_point = {}
+        self._i = 0  # some unique index to be associated with each point
+
     def _get_max_tasks(self):
         return self._max_tasks or _get_ncores(self.executor)
 
-    def _do_raise(self, e, x):
-        tb = self.tracebacks[x]
+    def _do_raise(self, e, i):
+        tb = self.tracebacks[i]
+        x = self.index_to_point[i]
         raise RuntimeError(
             "An error occured while evaluating "
             f'"learner.function({x})". '
@@ -162,9 +173,14 @@ def do_log(self):
         return self.log is not None
 
     def _ask(self, n):
-        points = [
-            p for p in self.to_retry.keys() if p not in self.pending_points.values()
-        ][:n]
+        points = []
+        for i, index in enumerate(self.to_retry.keys()):
+            if i == n:
+                break
+            point = self.index_to_point[index]
+            if point not in self.pending_points.values():
+                points.append(point)
+
         loss_improvements = len(points) * [float("inf")]
         if len(points) < n:
             new_points, new_losses = self.learner.ask(n - len(points))
@@ -198,20 +214,22 @@ def overhead(self):
     def _process_futures(self, done_futs):
         for fut in done_futs:
             x = self.pending_points.pop(fut)
+            i = _key_by_value(self.index_to_point, x)  # O(N)
             try:
                 y = fut.result()
                 t = time.time() - fut.start_time  # total execution time
             except Exception as e:
-                self.tracebacks[x] = traceback.format_exc()
-                self.to_retry[x] = self.to_retry.get(x, 0) + 1
-                if self.to_retry[x] > self.retries:
-                    self.to_retry.pop(x)
+                self.tracebacks[i] = traceback.format_exc()
+                self.to_retry[i] = self.to_retry.get(i, 0) + 1
+                if self.to_retry[i] > self.retries:
+                    self.to_retry.pop(i)
                     if self.raise_if_retries_exceeded:
-                        self._do_raise(e, x)
+                        self._do_raise(e, i)
             else:
                 self._elapsed_function_time += t / self._get_max_tasks()
-                self.to_retry.pop(x, None)
-                self.tracebacks.pop(x, None)
+                self.to_retry.pop(i, None)
+                self.tracebacks.pop(i, None)
+                self.index_to_point.pop(i)
                 if self.do_log:
                     self.log.append(("tell", x, y))
                 self.learner.tell(x, y)
@@ -232,6 +250,12 @@ def _get_futures(self):
             fut = self._submit(x)
             fut.start_time = start_time
             self.pending_points[fut] = x
+            i = _key_by_value(self.index_to_point, x)  # O(N)
+            if i is None:
+                # `x` is not a value in `self.index_to_point`
+                self._i += 1
+                i = self._i
+            self.index_to_point[i] = x
 
         # Collect and results and add them to the learner
         futures = list(self.pending_points.keys())