diff --git a/tests/suites/test_suite_ecp.data b/tests/suites/test_suite_ecp.data
index 17ad8aa..2edc519 100644
--- a/tests/suites/test_suite_ecp.data
+++ b/tests/suites/test_suite_ecp.data
@@ -159,6 +159,12 @@
 ECP small check pubkey #10
 ecp_small_check_pub:10:25:1:POLARSSL_ERR_ECP_INVALID_KEY
 
+ECP check pubkey Montgomery #1 (too big)
+ecp_check_pub_mx:POLARSSL_ECP_DP_M255:"010000000000000000000000000000000000000000000000000000000000000000":POLARSSL_ERR_ECP_INVALID_KEY
+
+ECP check pubkey Montgomery #2 (biggest)
+ecp_check_pub_mx:POLARSSL_ECP_DP_M255:"FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF":0
+
 ECP write binary #0 (zero, bad format)
 depends_on:POLARSSL_ECP_DP_SECP192R1_ENABLED
 ecp_write_binary:POLARSSL_ECP_DP_SECP192R1:"01":"01":"00":POLARSSL_ECP_PF_UNKNOWN:"00":1:POLARSSL_ERR_ECP_BAD_INPUT_DATA
@@ -271,9 +277,49 @@
 depends_on:POLARSSL_ECP_DP_SECP521R1_ENABLED
 ecp_tls_write_read_group:POLARSSL_ECP_DP_SECP521R1
 
-ECP check privkey
+ECP check privkey #1 (short weierstrass, too small)
 depends_on:POLARSSL_ECP_DP_SECP192R1_ENABLED
-ecp_check_privkey:POLARSSL_ECP_DP_SECP192R1
+ecp_check_privkey:POLARSSL_ECP_DP_SECP192R1:"00":POLARSSL_ERR_ECP_INVALID_KEY
+
+ECP check privkey #2 (short weierstrass, smallest)
+depends_on:POLARSSL_ECP_DP_SECP192R1_ENABLED
+ecp_check_privkey:POLARSSL_ECP_DP_SECP192R1:"01":0
+
+ECP check privkey #3 (short weierstrass, biggest)
+depends_on:POLARSSL_ECP_DP_SECP192R1_ENABLED
+ecp_check_privkey:POLARSSL_ECP_DP_SECP192R1:"FFFFFFFFFFFFFFFFFFFFFFFF99DEF836146BC9B1B4D22830":0
+
+ECP check privkey #4 (short weierstrass, too big)
+depends_on:POLARSSL_ECP_DP_SECP192R1_ENABLED
+ecp_check_privkey:POLARSSL_ECP_DP_SECP192R1:"FFFFFFFFFFFFFFFFFFFFFFFF99DEF836146BC9B1B4D22831":POLARSSL_ERR_ECP_INVALID_KEY
+
+ECP check privkey #5 (montgomery, too big)
+depends_on:POLARSSL_ECP_DP_M255_ENABLED
+ecp_check_privkey:POLARSSL_ECP_DP_M255:"C000000000000000000000000000000000000000000000000000000000000000":POLARSSL_ERR_ECP_INVALID_KEY
+
+ECP check privkey #6 (montgomery, not big enough)
+depends_on:POLARSSL_ECP_DP_M255_ENABLED
+ecp_check_privkey:POLARSSL_ECP_DP_M255:"3FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF0":POLARSSL_ERR_ECP_INVALID_KEY
+
+ECP check privkey #7 (montgomery, msb OK)
+depends_on:POLARSSL_ECP_DP_M255_ENABLED
+ecp_check_privkey:POLARSSL_ECP_DP_M255:"4000000000000000000000000000000000000000000000000000000000000000":0
+
+ECP check privkey #8 (montgomery, bit 0 set)
+depends_on:POLARSSL_ECP_DP_M255_ENABLED
+ecp_check_privkey:POLARSSL_ECP_DP_M255:"4000000000000000000000000000000000000000000000000000000000000001":POLARSSL_ERR_ECP_INVALID_KEY
+
+ECP check privkey #9 (montgomery, bit 1 set)
+depends_on:POLARSSL_ECP_DP_M255_ENABLED
+ecp_check_privkey:POLARSSL_ECP_DP_M255:"4000000000000000000000000000000000000000000000000000000000000002":POLARSSL_ERR_ECP_INVALID_KEY
+
+ECP check privkey #10 (montgomery, bit 2 set)
+depends_on:POLARSSL_ECP_DP_M255_ENABLED
+ecp_check_privkey:POLARSSL_ECP_DP_M255:"4000000000000000000000000000000000000000000000000000000000000004":POLARSSL_ERR_ECP_INVALID_KEY
+
+ECP check privkey #11 (montgomery, OK)
+depends_on:POLARSSL_ECP_DP_M255_ENABLED
+ecp_check_privkey:POLARSSL_ECP_DP_M255:"7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF8":0
 
 ECP gen keypair
 depends_on:POLARSSL_ECP_DP_SECP192R1_ENABLED
diff --git a/tests/suites/test_suite_ecp.function b/tests/suites/test_suite_ecp.function
index cb93e85..626d2bf 100644
--- a/tests/suites/test_suite_ecp.function
+++ b/tests/suites/test_suite_ecp.function
@@ -189,6 +189,27 @@
 /* END_CASE */
 
 /* BEGIN_CASE */
+void ecp_check_pub_mx( int grp_id, char *key_hex, int ret )
+{
+    ecp_group grp;
+    ecp_point P;
+
+    ecp_group_init( &grp );
+    ecp_point_init( &P );
+
+    TEST_ASSERT( ecp_use_known_dp( &grp, grp_id ) == 0 );
+
+    TEST_ASSERT( mpi_read_string( &P.X, 16, key_hex ) == 0 );
+    TEST_ASSERT( mpi_lset( &P.Z, 1 ) == 0 );
+
+    TEST_ASSERT( ecp_check_pubkey( &grp, &P ) == ret );
+
+    ecp_group_free( &grp );
+    ecp_point_free( &P );
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
 void ecp_test_vect( int id, char *dA_str, char *xA_str, char *yA_str,
                     char *dB_str, char *xB_str, char *yB_str, char *xZ_str,
                     char *yZ_str )
@@ -490,7 +511,7 @@
 /* END_CASE */
 
 /* BEGIN_CASE */
-void ecp_check_privkey( int id )
+void ecp_check_privkey( int id, char *key_hex, int ret )
 {
     ecp_group grp;
     mpi d;
@@ -499,12 +520,9 @@
     mpi_init( &d );
 
     TEST_ASSERT( ecp_use_known_dp( &grp, id ) == 0 );
+    TEST_ASSERT( mpi_read_string( &d, 16, key_hex ) == 0 );
 
-    TEST_ASSERT( mpi_lset( &d, 0 ) == 0 );
-    TEST_ASSERT( ecp_check_privkey( &grp, &d ) == POLARSSL_ERR_ECP_INVALID_KEY );
-
-    TEST_ASSERT( mpi_copy( &d, &grp.N ) == 0 );
-    TEST_ASSERT( ecp_check_privkey( &grp, &d ) == POLARSSL_ERR_ECP_INVALID_KEY );
+    TEST_ASSERT( ecp_check_privkey( &grp, &d ) == ret );
 
     ecp_group_free( &grp );
     mpi_free( &d );