diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 09fbd0c..4d70a3f 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -19,6 +19,7 @@ jobs:
           - "3.11"
           - "3.12"
           - "3.13"
+          - "pypy"
 
     runs-on: ${{ matrix.platform }}
     steps:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7a437c8..6e0d148 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Moved `maturin` dependency from main project dependencies to development dependencies
   since it's only needed for development tasks ([88](https://github.com/trailofbits/rfc3161-client/pull/88))
 
+### Fixed
+
+- The project now correctly runs tests with PyPy
+  ([89](https://github.com/trailofbits/rfc3161-client/pull/89))
+
 ## [0.1.1] - 2024-12-10
 
 ### Changed
diff --git a/Cargo.lock b/Cargo.lock
index 16b6ea8..0e6bb99 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -372,6 +372,7 @@ dependencies = [
  "hex",
  "openssl",
  "pyo3",
+ "pyo3-build-config",
  "rand",
  "self_cell",
  "sha2",
diff --git a/rust/Cargo.toml b/rust/Cargo.toml
index 95cb227..ac944c0 100644
--- a/rust/Cargo.toml
+++ b/rust/Cargo.toml
@@ -21,5 +21,8 @@ rand = "0.8.5"
 cryptography-x509.workspace = true
 openssl = { version = "0.10.68", features = ["vendored"] }
 
+[build-dependencies]
+pyo3-build-config = { version = "0.23.1", features = ["resolve-config"] }
+
 [features]
 extension-module = ["pyo3/extension-module"]
diff --git a/rust/build.rs b/rust/build.rs
new file mode 100644
index 0000000..0475124
--- /dev/null
+++ b/rust/build.rs
@@ -0,0 +1,3 @@
+fn main() {
+    pyo3_build_config::use_pyo3_cfgs();
+}
diff --git a/rust/src/lib.rs b/rust/src/lib.rs
index cf3f98f..1a2d02b 100644
--- a/rust/src/lib.rs
+++ b/rust/src/lib.rs
@@ -760,6 +760,9 @@ mod _rust {
     }
 }
 
+// We cannot run tests when used with PyPy because it lacks Py_Initialize
+// https://github.com/pypy/pypy/issues/3836
+#[cfg(not(PyPy))]
 #[cfg(test)]
 mod tests {
     use super::OwnedTimeStampResp;