diff --git a/library/pkwrite.h b/library/pkwrite.h
index bc40437..8cfa64b 100644
--- a/library/pkwrite.h
+++ b/library/pkwrite.h
@@ -27,6 +27,10 @@
 
 #include "mbedtls/pk.h"
 
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+#include "psa/crypto.h"
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+
 /*
  * Max sizes of key per types. Shown as tag + len (+ content).
  */
@@ -74,6 +78,19 @@
 #endif /* MBEDTLS_RSA_C */
 
 #if defined(MBEDTLS_PK_HAVE_ECC_KEYS)
+
+/* Find the maximum number of bytes necessary to store an EC point. When USE_PSA
+ * is defined this means looking for the maximum between PSA and built-in
+ * supported curves. */
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+#define MBEDTLS_PK_MAX_ECC_BYTES   (PSA_BITS_TO_BYTES(PSA_VENDOR_ECC_MAX_CURVE_BITS) > \
+                                    MBEDTLS_ECP_MAX_BYTES ? \
+                                    PSA_BITS_TO_BYTES(PSA_VENDOR_ECC_MAX_CURVE_BITS) : \
+                                    MBEDTLS_ECP_MAX_BYTES)
+#else /* MBEDTLS_USE_PSA_CRYPTO */
+#define MBEDTLS_PK_MAX_ECC_BYTES   MBEDTLS_ECP_MAX_BYTES
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+
 /*
  * EC public keys:
  *  SubjectPublicKeyInfo  ::=  SEQUENCE  {      1 + 2
@@ -85,7 +102,7 @@
  *                                            + 2 * ECP_MAX (coords)    [1]
  *  }
  */
-#define MBEDTLS_PK_ECP_PUB_DER_MAX_BYTES    (30 + 2 * 66)
+#define MBEDTLS_PK_ECP_PUB_DER_MAX_BYTES    (30 + 2 * MBEDTLS_PK_MAX_ECC_BYTES)
 
 /*
  * EC private keys:
@@ -96,7 +113,7 @@
  *      publicKey  [1] BIT STRING OPTIONAL      1 + 2 + [1] above
  *    }
  */
-#define MBEDTLS_PK_ECP_PRV_DER_MAX_BYTES    (29 + 3 * 66)
+#define MBEDTLS_PK_ECP_PRV_DER_MAX_BYTES    (29 + 3 * MBEDTLS_PK_MAX_ECC_BYTES)
 
 #else /* MBEDTLS_PK_HAVE_ECC_KEYS */