diff --git a/library/pk_internal.h b/library/pk_internal.h
index 642a0c7..3d5adf8 100644
--- a/library/pk_internal.h
+++ b/library/pk_internal.h
@@ -98,13 +98,13 @@
         }
         opaque_key_type = psa_get_key_type(&opaque_attrs);
         curve = PSA_KEY_TYPE_ECC_GET_FAMILY(opaque_key_type);
-        id = mbedtls_ecc_group_from_psa(curve, psa_get_key_bits(&opaque_attrs), 0);
+        id = mbedtls_ecc_group_from_psa(curve, psa_get_key_bits(&opaque_attrs));
         psa_reset_key_attributes(&opaque_attrs);
     } else
 #endif /* MBEDTLS_USE_PSA_CRYPTO */
     {
 #if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
-        id = mbedtls_ecc_group_from_psa(pk->ec_family, pk->ec_bits, 0);
+        id = mbedtls_ecc_group_from_psa(pk->ec_family, pk->ec_bits);
 #else /* MBEDTLS_PK_USE_PSA_EC_DATA */
         id = mbedtls_pk_ec_ro(*pk)->grp.id;
 #endif /* MBEDTLS_PK_USE_PSA_EC_DATA */
diff --git a/library/pkparse.c b/library/pkparse.c
index ef3aff2..5f95545 100644
--- a/library/pkparse.c
+++ b/library/pkparse.c
@@ -250,7 +250,7 @@
     mbedtls_ecp_group_id ecp_group_id;
     int ret;
 
-    ecp_group_id = mbedtls_ecc_group_from_psa(pk->ec_family, pk->ec_bits, 0);
+    ecp_group_id = mbedtls_ecc_group_from_psa(pk->ec_family, pk->ec_bits);
 
     mbedtls_ecp_keypair_init(&ecp_key);
     ret = mbedtls_ecp_group_load(&(ecp_key.grp), ecp_group_id);
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index d393109..850f206 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -5708,7 +5708,7 @@
     psa_ecc_family_t curve = PSA_KEY_TYPE_ECC_GET_FAMILY(
         slot->attr.type);
     mbedtls_ecp_group_id grp_id =
-        mbedtls_ecc_group_from_psa(curve, bits, 0);
+        mbedtls_ecc_group_from_psa(curve, bits);
 
     if (grp_id == MBEDTLS_ECP_DP_NONE) {
         ret = MBEDTLS_ERR_ASN1_INVALID_DATA;
diff --git a/library/psa_crypto_ecp.c b/library/psa_crypto_ecp.c
index 3f2ec23..20ef29c 100644
--- a/library/psa_crypto_ecp.c
+++ b/library/psa_crypto_ecp.c
@@ -41,6 +41,7 @@
     psa_status_t status;
     mbedtls_ecp_keypair *ecp = NULL;
     size_t curve_bytes = data_length;
+    size_t curve_bits_check;
     int explicit_bits = (curve_bits != 0);
 
     if (PSA_KEY_TYPE_IS_PUBLIC_KEY(type) &&
@@ -84,7 +85,7 @@
 
     /* Load the group. */
     grp_id = mbedtls_ecc_group_from_psa(PSA_KEY_TYPE_ECC_GET_FAMILY(type),
-                                        curve_bits, !explicit_bits);
+                                        curve_bits);
     if (grp_id == MBEDTLS_ECP_DP_NONE) {
         /* We can't distinguish between a nonsensical family/size combination
          * (which would warrant PSA_ERROR_INVALID_ARGUMENT) and a
@@ -96,6 +97,17 @@
         goto exit;
     }
 
+    /* Get the exact number of bits which are necessary for this key. This is
+     * used to validate the "curve_bits" input parameter (only in case it was
+     * provided).
+     * Note: we intentionally ignore the return value of mbedtls_ecc_group_to_psa()
+     *       because we are only interested in the curve's bit size. */
+    mbedtls_ecc_group_to_psa(grp_id, &curve_bits_check);
+    if (explicit_bits && (curve_bits_check != curve_bits)) {
+        status = PSA_ERROR_NOT_SUPPORTED;
+        goto exit;
+    }
+
     status = mbedtls_to_psa_error(
         mbedtls_ecp_group_load(&ecp->grp, grp_id));
     if (status != PSA_SUCCESS) {
@@ -285,7 +297,7 @@
     psa_ecc_family_t curve = PSA_KEY_TYPE_ECC_GET_FAMILY(
         attributes->core.type);
     mbedtls_ecp_group_id grp_id =
-        mbedtls_ecc_group_from_psa(curve, attributes->core.bits, 0);
+        mbedtls_ecc_group_from_psa(curve, attributes->core.bits);
 
     const mbedtls_ecp_curve_info *curve_info =
         mbedtls_ecp_curve_info_from_grp_id(grp_id);
diff --git a/library/psa_util.c b/library/psa_util.c
index f4685db..abd7a5f 100644
--- a/library/psa_util.c
+++ b/library/psa_util.c
@@ -253,8 +253,7 @@
 }
 
 mbedtls_ecp_group_id mbedtls_ecc_group_from_psa(psa_ecc_family_t curve,
-                                                size_t bits,
-                                                int bits_is_sloppy)
+                                                size_t bits)
 {
     switch (curve) {
         case PSA_ECC_FAMILY_SECP_R1:
@@ -277,12 +276,8 @@
 #endif
 #if defined(PSA_WANT_ECC_SECP_R1_521)
                 case 521:
-                    return MBEDTLS_ECP_DP_SECP521R1;
                 case 528:
-                    if (bits_is_sloppy) {
-                        return MBEDTLS_ECP_DP_SECP521R1;
-                    }
-                    break;
+                    return MBEDTLS_ECP_DP_SECP521R1;
 #endif
             }
             break;
@@ -308,12 +303,8 @@
             switch (bits) {
 #if defined(PSA_WANT_ECC_MONTGOMERY_255)
                 case 255:
-                    return MBEDTLS_ECP_DP_CURVE25519;
                 case 256:
-                    if (bits_is_sloppy) {
-                        return MBEDTLS_ECP_DP_CURVE25519;
-                    }
-                    break;
+                    return MBEDTLS_ECP_DP_CURVE25519;
 #endif
 #if defined(PSA_WANT_ECC_MONTGOMERY_448)
                 case 448:
@@ -340,7 +331,6 @@
             break;
     }
 
-    (void) bits_is_sloppy;
     return MBEDTLS_ECP_DP_NONE;
 }
 #endif /* PSA_WANT_KEY_TYPE_ECC_PUBLIC_KEY */