diff --git a/brainbox/singlecell/singlecell.py b/brainbox/singlecell/singlecell.py
index 45621420c..1e90497eb 100644
--- a/brainbox/singlecell/singlecell.py
+++ b/brainbox/singlecell/singlecell.py
@@ -24,7 +24,8 @@ def acorr(spike_times, bin_size=None, window_size=None):
     Returns an `(winsize_samples,)` array with the auto-correlogram.
 
     """
-    xc = xcorr(spike_times, np.zeros_like(spike_times), bin_size=bin_size, window_size=window_size)
+    xc = xcorr(spike_times, np.zeros_like(spike_times, dtype=np.int32),
+               bin_size=bin_size, window_size=window_size)
     return xc[0, 0, :]
 
 
diff --git a/brainbox/tests/test_singlecell.py b/brainbox/tests/test_singlecell.py
index 67f9a1f6f..8f978e413 100644
--- a/brainbox/tests/test_singlecell.py
+++ b/brainbox/tests/test_singlecell.py
@@ -16,6 +16,18 @@ def test_acorr_0(self):
 
         self.assertTrue(np.allclose(c, c_expected))
 
+    def test_acorr_1(self):
+        spike_times = np.array([0, 10, 10, 20], dtype=np.float64)
+        bin_size = 1
+        winsize_bins = 2 * 3 + 1
+
+        c_expected = np.zeros(7, dtype=np.float64)
+        c_expected[3] = 1
+
+        c = acorr(spike_times, bin_size=bin_size, window_size=winsize_bins)
+
+        self.assertTrue(np.allclose(c, c_expected))
+
 
 class TestPeths(unittest.TestCase):
     def test_peths_synthetic(self):