diff --git a/lib/Crypto/PublicKey/ECC.py b/lib/Crypto/PublicKey/ECC.py
index 4a7c86ccf..5bce31f73 100644
--- a/lib/Crypto/PublicKey/ECC.py
+++ b/lib/Crypto/PublicKey/ECC.py
@@ -43,7 +43,6 @@
 from Crypto.Util.asn1 import (DerObjectId, DerOctetString, DerSequence,
                               DerBitString)
 
-from Crypto.IO import PKCS8, PEM
 from Crypto.PublicKey import (_expand_subject_public_key_info,
                               _create_subject_public_key_info,
                               _extract_subject_public_key_info)
@@ -589,6 +588,8 @@ def _export_private_der(self, include_ec_params=True):
         return DerSequence(seq).encode()
 
     def _export_pkcs8(self, **kwargs):
+        from Crypto.IO import PKCS8
+
         if kwargs.get('passphrase', None) is not None and 'protection' not in kwargs:
             raise ValueError("At least the 'protection' parameter should be present")
 
@@ -601,18 +602,26 @@ def _export_pkcs8(self, **kwargs):
         return result
 
     def _export_public_pem(self, compress):
+        from Crypto.IO import PEM
+
         encoded_der = self._export_subjectPublicKeyInfo(compress)
         return PEM.encode(encoded_der, "PUBLIC KEY")
 
     def _export_private_pem(self, passphrase, **kwargs):
+        from Crypto.IO import PEM
+
         encoded_der = self._export_private_der()
         return PEM.encode(encoded_der, "EC PRIVATE KEY", passphrase, **kwargs)
 
     def _export_private_clear_pkcs8_in_clear_pem(self):
+        from Crypto.IO import PEM
+
         encoded_der = self._export_pkcs8()
         return PEM.encode(encoded_der, "PRIVATE KEY")
 
     def _export_private_encrypted_pkcs8_in_clear_pem(self, passphrase, **kwargs):
+        from Crypto.IO import PEM
+
         assert passphrase
         if 'protection' not in kwargs:
             raise ValueError("At least the 'protection' parameter should be present")
@@ -950,6 +959,7 @@ def _import_private_der(encoded, passphrase, curve_oid=None):
 
 
 def _import_pkcs8(encoded, passphrase):
+    from Crypto.IO import PKCS8
 
     # From RFC5915, Section 1:
     #
@@ -1106,6 +1116,8 @@ def import_key(encoded, passphrase=None):
     .. _`OpenSSH 6.5+`: https://flak.tedunangst.com/post/new-openssh-key-format-and-bcrypt-pbkdf
     """
 
+    from Crypto.IO import PEM
+
     encoded = tobytes(encoded)
     if passphrase is not None:
         passphrase = tobytes(passphrase)
diff --git a/lib/Crypto/PublicKey/RSA.py b/lib/Crypto/PublicKey/RSA.py
index 194653a51..98ee8b00b 100644
--- a/lib/Crypto/PublicKey/RSA.py
+++ b/lib/Crypto/PublicKey/RSA.py
@@ -35,7 +35,6 @@
 import struct
 
 from Crypto import Random
-from Crypto.IO import PKCS8, PEM
 from Crypto.Util.py3compat import tobytes, bord, tostr
 from Crypto.Util.asn1 import DerSequence
 
@@ -333,6 +332,8 @@ def export_key(self, format='PEM', passphrase=None, pkcs=1,
                 if format == 'DER' and passphrase:
                     raise ValueError("PKCS#1 private key cannot be encrypted")
             else:  # PKCS#8
+                from Crypto.IO import PKCS8
+
                 if format == 'PEM' and protection is None:
                     key_type = 'PRIVATE KEY'
                     binary_key = PKCS8.wrap(binary_key, oid, None)
@@ -353,6 +354,8 @@ def export_key(self, format='PEM', passphrase=None, pkcs=1,
         if format == 'DER':
             return binary_key
         if format == 'PEM':
+            from Crypto.IO import PEM
+
             pem_str = PEM.encode(binary_key, key_type, passphrase, randfunc)
             return tobytes(pem_str)
 
@@ -652,6 +655,8 @@ def _import_x509_cert(encoded, *kwargs):
 
 
 def _import_pkcs8(encoded, passphrase):
+    from Crypto.IO import PKCS8
+
     k = PKCS8.unwrap(encoded, passphrase)
     if k[0] != oid:
         raise ValueError("No PKCS#8 encoded RSA key")
@@ -741,6 +746,8 @@ def import_key(extern_key, passphrase=None):
     .. _`OpenSSH 6.5`: https://flak.tedunangst.com/post/new-openssh-key-format-and-bcrypt-pbkdf
     """
 
+    from Crypto.IO import PEM
+
     extern_key = tobytes(extern_key)
     if passphrase is not None:
         passphrase = tobytes(passphrase)
diff --git a/lib/Crypto/Util/_raw_api.py b/lib/Crypto/Util/_raw_api.py
index 0521ff62f..77a992ef7 100644
--- a/lib/Crypto/Util/_raw_api.py
+++ b/lib/Crypto/Util/_raw_api.py
@@ -30,7 +30,6 @@
 
 import abc
 import sys
-import platform
 from Crypto.Util.py3compat import byte_string
 from Crypto.Util._file_system import pycryptodome_filename
 
@@ -79,7 +78,7 @@ def address_of(self):
     # Note that PyPy ships with an old version of pycparser so we can keep
     # using cffi there.
     # See https://github.com/Legrandin/pycryptodome/issues/228
-    if platform.python_implementation() != "PyPy" and sys.flags.optimize == 2:
+    if '__pypy__' not in sys.builtin_module_names and sys.flags.optimize == 2:
         raise ImportError("CFFI with optimize=2 fails due to pycparser bug.")
 
     from cffi import FFI