diff --git a/pyproject.toml b/pyproject.toml
index 6dcfeb7..42f5fab 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,6 +7,7 @@ requires-python = ">=3.11"
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]
+pythonpath = ["src"]
 
 [project.scripts]
 tea3-linear-bias = "tea3.tea3linearbias:main"
diff --git a/src/tea3/tea3.py b/src/tea3/tea3.py
index 6dd5e79..5d604be 100644
--- a/src/tea3/tea3.py
+++ b/src/tea3/tea3.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 from dataclasses import dataclass
 from typing import Sequence
 
-from .constants import TEA3_LUT_A, TEA3_LUT_B, TEA3_SBOX
+from tea3.constants import TEA3_LUT_A, TEA3_LUT_B, TEA3_SBOX
 
 MASK32 = 0xFFFFFFFF
 MASK64 = 0xFFFFFFFFFFFFFFFF
diff --git a/src/tea3/tea3differentialbias.py b/src/tea3/tea3differentialbias.py
index 3766b51..c83d43f 100644
--- a/src/tea3/tea3differentialbias.py
+++ b/src/tea3/tea3differentialbias.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 from dataclasses import dataclass
 from random import Random
 
-from .tea3 import Tea3
+from tea3.tea3 import Tea3
 
 
 def rand_key(rng: Random) -> list[int]:
diff --git a/src/tea3/tea3linearbias.py b/src/tea3/tea3linearbias.py
index e6c6a2a..664b31d 100644
--- a/src/tea3/tea3linearbias.py
+++ b/src/tea3/tea3linearbias.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 from dataclasses import dataclass
 from random import Random
 
-from .tea3 import Tea3
+from tea3.tea3 import Tea3
 
 
 def rand_key(rng: Random) -> list[int]: