diff --git a/polyomino/problem.py b/polyomino/problem.py
index 9c40c4a..5e4c9e2 100644
--- a/polyomino/problem.py
+++ b/polyomino/problem.py
@@ -1,6 +1,7 @@
 import numpy as np
 
 from exact_cover import get_exact_cover
+from exact_cover.error import NoSolution
 
 from .error import CantPlaceSinglePiece
 from .solution import Solution
@@ -60,7 +61,10 @@ def make_problem(self):
 
     def solve(self):
         self.make_problem()
-        solution = get_exact_cover(self.array)
+        try:
+            solution = get_exact_cover(self.array)
+        except NoSolution:
+            return None
         tiling = [self.key[s] for s in solution]
         if tiling:
             return Solution(tiling, self.board)
diff --git a/pyproject.toml b/pyproject.toml
index 7bc2135..112ac61 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "polyomino"
-version = "0.6.6"
+version = "0.7.0"
 description = "Solve polyomino tiling problems."
 readme = "README.md"
 authors = ["Jack Grahl <jack.grahl@gmail.com>"]
@@ -8,8 +8,7 @@ license = "MIT"
 
 [tool.poetry.dependencies]
 python = "^3.7.1"
-exact-cover = "0.4.3"
-numpy = "^1.20"
+exact-cover = "1.3.0"
 pretty-poly = "0.2.0"
 
 [tool.poetry.dev-dependencies]
@@ -17,12 +16,14 @@ pytest = "^6.2.1"
 hypothesis = "^6.0.2"
 pytest-profiling = "^1.7.0"
 black = "^21.6b0"
-pytest-fail-slow = "^0.1.0"
 
 [tool.poetry.scripts]
 test = 'run_tests:run_tests'
 doctest = 'run_tests:run_doctests'
 
+[tool.poetry.group.dev.dependencies]
+pytest-fail-slow = ">=0.2.0,<0.3.0"
+
 [build-system]
 requires = ["poetry-core>=1.0.0"]
 build-backend = "poetry.core.masonry.api"