diff --git a/Lib/fontTools/misc/bezierTools.py b/Lib/fontTools/misc/bezierTools.py
index 1b37ade8d..2021f2443 100644
--- a/Lib/fontTools/misc/bezierTools.py
+++ b/Lib/fontTools/misc/bezierTools.py
@@ -631,7 +631,14 @@ def splitCubicAtT(pt1, pt2, pt3, pt4, *ts):
         ((77.3438, 56.25), (85.9375, 43.75), (93.75, 25), (100, 0))
     """
     a, b, c, d = calcCubicParameters(pt1, pt2, pt3, pt4)
-    return _splitCubicAtT(a, b, c, d, *ts)
+    split = _splitCubicAtT(a, b, c, d, *ts)
+
+    # the split impl can introduce floating point errors; we know the first
+    # segment should always start at pt1 and the last segment should end at pt4,
+    # so we set those values directly before returning.
+    split[0] = (pt1, *split[0][1:])
+    split[-1] = (*split[-1][:-1], pt4)
+    return split
 
 
 @cython.locals(
diff --git a/Tests/misc/bezierTools_test.py b/Tests/misc/bezierTools_test.py
index 6107a39df..fe7a3d214 100644
--- a/Tests/misc/bezierTools_test.py
+++ b/Tests/misc/bezierTools_test.py
@@ -144,6 +144,12 @@ def test_splitCubicAtT():
     ]
 
 
+def test_splitCubicAtT_robustness():
+    segment = ((-103, -231), (-61, -240), (-31.009, -245), (6, -245))
+    (_, tail) = splitCubicAtT(*segment, 0.386637)
+    assert tail[-1] == segment[-1]
+
+
 def test_solveCubic():
     assert solveCubic(1, 1, -6, 0) == [-3.0, -0.0, 2.0]
     assert solveCubic(-10.0, -9.0, 48.0, -29.0) == [-2.9, 1.0, 1.0]