diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py
index 70ed25d..a6acb07 100644
--- a/src/cryptography/hazmat/backends/openssl/backend.py
+++ b/src/cryptography/hazmat/backends/openssl/backend.py
@@ -140,6 +140,12 @@
         _encode_asn1_str(backend, pp[0], r),
     )
     assert extension != backend._ffi.NULL
+
+    # Release acquired memory.
+    backend._lib.OPENSSL_free(pp[0])
+    pp[0] = backend._ffi.NULL
+
+    # Return the wrapped extension.
     return extension