diff --git a/pyproject.toml b/pyproject.toml
index 304a219..b8cdd73 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -26,8 +26,15 @@ classifiers = [
     "Topic :: Scientific/Engineering",
     "Typing :: Typed",
 ]
+# `~=0.1` is `>=0.1, ==0.*`: the fastfields distributions are versioned and
+# released together off the same 0.1 line (versioningit `default-tag = "0.1"`),
+# so a bare, unversioned dependency would happily resolve to a future 1.x whose
+# ABI/enums no longer match this wrapper. The floor is deliberately the line,
+# not an exact pin, so in-development builds (`0.1+<distance>.g<rev>`, and the
+# backend-labelled release wheels `0.1+cpu` / `0.1+cu128`) all satisfy it and
+# the constraint does not go stale on every commit.
 dependencies = [
-    "fastfields-dlpack",
+    "fastfields-dlpack~=0.1",
     "numpy",
 ]