diff --git a/cereeberus/cereeberus/compute/computereeb.py b/cereeberus/cereeberus/compute/computereeb.py
index 7a569b4..16c5da2 100644
--- a/cereeberus/cereeberus/compute/computereeb.py
+++ b/cereeberus/cereeberus/compute/computereeb.py
@@ -4,6 +4,12 @@
 
 from ..reeb.lowerstar import LowerStar
 
+# Tolerance for treating two filtration values as float64-indistinguishable
+# (i.e. within ~1 ULP of each other, the scale of floating-point rounding
+# noise. It is not intended to merge genuinely distinct nearby values).
+_ULP_RTOL = 1e-9
+_ULP_ATOL = 1e-12
+
 
 class _DenseUnionFind:
     """Small array-backed union-find used by the exact slice sweep."""
diff --git a/pyproject.toml b/pyproject.toml
index d70d00e..f21a1d9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -20,7 +20,7 @@ dependencies = ["numpy",
             "matplotlib",
             "pandas",
             "scipy", 
-            "pulp",
+            "pulp<4",
             "gudhi",
             "scikit-learn"
             ]
@@ -34,4 +34,4 @@ cereeberus = ["data"]
 [project.urls]
 repository = "https://github.com/MunchLab/ceREEBerus"
 homepage = "https://munchlab.github.io/ceREEBerus/"
-documentation = "https://munchlab.github.io/ceREEBerus/"
\ No newline at end of file
+documentation = "https://munchlab.github.io/ceREEBerus/"
diff --git a/requirements.txt b/requirements.txt
index e1fa66f..a462920 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,7 @@ networkx
 matplotlib
 pandas
 scipy
-pulp
+pulp<4
 gudhi
 sphinx
 nbsphinx