diff --git a/requirements.txt b/requirements.txt
index d6df3a4..73c0075 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-numpy==1.15.1
-scipy==1.0.1
-ortools==6.9.5824
-packaging==16.8
\ No newline at end of file
+numpy>=1.15.1
+scipy>=1.0.1
+ortools>=6.9.5824
+packaging>=16.8
\ No newline at end of file
diff --git a/seriate.py b/seriate.py
index 94305d5..d9859a2 100644
--- a/seriate.py
+++ b/seriate.py
@@ -11,8 +11,10 @@
 ortools_version = Version(ortools.__version__)
 ortools6 = Version("6.0.0") <= ortools_version < Version("7")
 ortools7 = Version("7.0.0") <= ortools_version < Version("8")
-if not ortools6 and not ortools7:
-    raise ImportError("No valid version of ortools installed. Please install ortools 6 or 7.")
+ortools8 = Version("8.0.0") <= ortools_version < Version("9")
+ortools9 = Version("9.0.0") <= ortools_version < Version("10")
+if not ortools6 and not ortools7 and not ortools8 and not ortools9:
+    raise ImportError("No valid version of ortools installed. Please install ortools 6 or 7 or 8 or 9.")
 
 
 class IncompleteSolutionError(Exception):
@@ -101,12 +103,12 @@ def _seriate(dists: numpy.ndarray, approximation_multiplier=1000, timeout=2.0) -
 
     if ortools6:
         routing = pywrapcp.RoutingModel(size + 1, 1, size)
-    elif ortools7:
+    elif ortools7 or ortools8 or ortools9:
         manager = pywrapcp.RoutingIndexManager(size + 1, 1, size)
         routing = pywrapcp.RoutingModel(manager)
 
     def dist_callback(x, y):
-        if ortools7:
+        if ortools7 or ortools8 or ortools9:
             x = manager.IndexToNode(x)
             y = manager.IndexToNode(y)
         if x == size or y == size or x == y:
@@ -125,7 +127,7 @@ def dist_callback(x, y):
         routing.SetArcCostEvaluatorOfAllVehicles(dist_callback)
         search_parameters = pywrapcp.RoutingModel.DefaultSearchParameters()
         search_parameters.time_limit_ms = int(timeout * 1000)
-    elif ortools7:
+    elif ortools7 or ortools8 or ortools9:
         routing.SetArcCostEvaluatorOfAllVehicles(routing.RegisterTransitCallback(dist_callback))
         search_parameters = pywrapcp.DefaultRoutingSearchParameters()
         search_parameters.time_limit.FromMilliseconds(int(timeout * 1000))
@@ -142,7 +144,7 @@ def dist_callback(x, y):
     while not routing.IsEnd(index):
         if ortools6:
             node = routing.IndexToNode(index)
-        elif ortools7:
+        elif ortools7 or ortools8 or ortools9:
             node = manager.IndexToNode(index)
         if node < size:
             route.append(node)
diff --git a/setup.py b/setup.py
index 1b52a96..c66b4cd 100644
--- a/setup.py
+++ b/setup.py
@@ -20,7 +20,7 @@
     download_url="https://github.com/src-d/seriate",
     py_modules=["seriate"],
     keywords=["seriation"],
-    install_requires=["numpy>=1.0", "ortools>=6.7.4973,<8", "packaging>=16.0"],
+    install_requires=["numpy>=1.0", "ortools>=6.7.4973,<=9", "packaging>=16.0"],
     tests_require=["scipy>=1.0"],
     package_data={"": ["LICENSE.md", "README.md", "requirements.txt"]},
     classifiers=[
@@ -31,5 +31,6 @@
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
     ],
 )