diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index 1974e3f..e52953c 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -409,6 +409,63 @@
 Test mbedtls_mpi_cmp_mpi: large negative < 0 (1 limb)
 mbedtls_mpi_cmp_mpi:"-1230000000000000000":"0":-1
 
+Base test mbedtls_mpi_core_lt_ct #1
+mbedtls_mpi_core_lt_ct:"02B5":"02B5":0
+
+Base test mbedtls_mpi_core_lt_ct #2
+mbedtls_mpi_core_lt_ct:"02B5":"02B4":0
+
+Base test mbedtls_mpi_core_lt_ct #3
+mbedtls_mpi_core_lt_ct:"02B5":"02B6":1
+
+Base test mbedtls_mpi_core_lt_ct (length=0)
+mbedtls_mpi_core_lt_ct:"":"":0
+
+Base test mbedtls_mpi_core_lt_ct (corner case - 64 bit) #1
+mbedtls_mpi_core_lt_ct:"7FFFFFFFFFFFFFFF":"FF":0
+
+Base test mbedtls_mpi_core_lt_ct (corner case - 64 bit) #2
+mbedtls_mpi_core_lt_ct:"8000000000000000":"7FFFFFFFFFFFFFFF":0
+
+Base test mbedtls_mpi_core_lt_ct (corner case - 64 bit) #3
+mbedtls_mpi_core_lt_ct:"8000000000000000":"01":0
+
+Base test mbedtls_mpi_core_lt_ct (corner case - 64 bit) #4
+mbedtls_mpi_core_lt_ct:"8000000000000000":"00":0
+
+Base test mbedtls_mpi_core_lt_ct (corner case - 64 bit) #5
+mbedtls_mpi_core_lt_ct:"FFFFFFFFFFFFFFFF":"FF":0
+
+Base test mbedtls_mpi_core_lt_ct (corner case - 32 bit) #1
+mbedtls_mpi_core_lt_ct:"7FFFFFFF":"FF":0
+
+Base test mbedtls_mpi_core_lt_ct (corner case - 32 bit) #2
+mbedtls_mpi_core_lt_ct:"80000000":"7FFFFFFF":0
+
+Base test mbedtls_mpi_core_lt_ct (corner case - 32 bit) #3
+mbedtls_mpi_core_lt_ct:"80000000":"01":0
+
+Base test mbedtls_mpi_core_lt_ct (corner case - 32 bit) #4
+mbedtls_mpi_core_lt_ct:"80000000":"00":0
+
+Base test mbedtls_mpi_core_lt_ct (corner case - 32 bit) #5
+mbedtls_mpi_core_lt_ct:"FFFFFFFF":"FF":0
+
+Multi-limb mbedtls_mpi_core_lt_ct (X<Y, zero vs non-zero MS limb)
+mbedtls_mpi_core_lt_ct:"00FFFFFFFFFFFFFFFF":"01FFFFFFFFFFFFFFFF":1
+
+Multi-limb mbedtls_mpi_core_lt_ct (X>Y, equal MS limbs)
+mbedtls_mpi_core_lt_ct:"EEFFFFFFFFFFFFFFFF":"EEFFFFFFFFFFFFFFF1":0
+
+Multi-limb mbedtls_mpi_core_lt_ct (X=Y)
+mbedtls_mpi_core_lt_ct:"EEFFFFFFFFFFFFFFFF":"EEFFFFFFFFFFFFFFFF":0
+
+Multi-limb mbedtls_mpi_core_lt_ct (Alternating limbs) #1
+mbedtls_mpi_core_lt_ct:"11FFFFFFFFFFFFFFFF":"FF1111111111111111":1
+
+Multi-limb mbedtls_mpi_core_lt_ct (Alternating limbs) #2
+mbedtls_mpi_core_lt_ct:"FF1111111111111111":"11FFFFFFFFFFFFFFFF":0
+
 Base test mbedtls_mpi_lt_mpi_ct #1
 mbedtls_mpi_lt_mpi_ct:1:"2B5":1:"2B5":0:0
 
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index b0d947c..ff87ea4 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -2,6 +2,8 @@
 #include "mbedtls/bignum.h"
 #include "mbedtls/entropy.h"
 #include "bignum_core.h"
+#include "constant_time_internal.h"
+#include "test/constant_flow.h"
 
 #if MBEDTLS_MPI_MAX_BITS > 792
 #define MPI_MAX_BITS_LARGER_THAN_792
@@ -608,6 +610,42 @@
 /* END_CASE */
 
 /* BEGIN_CASE */
+void mbedtls_mpi_core_lt_ct( data_t * input_X, data_t * input_Y, int input_ret )
+{
+    #define MAX_LEN 64
+    mbedtls_mpi_uint X[MAX_LEN];
+    mbedtls_mpi_uint Y[MAX_LEN];
+    unsigned exp_ret = input_ret;
+    unsigned ret;
+    size_t len = CHARS_TO_LIMBS(
+                    input_X->len > input_Y->len ? input_X->len : input_Y->len );
+
+    TEST_ASSERT( len <= MAX_LEN );
+
+    TEST_ASSERT( mbedtls_mpi_core_read_be( X, len, input_X->x, input_X->len )
+                 == 0 );
+    TEST_ASSERT( mbedtls_mpi_core_read_be( Y, len, input_Y->x, input_Y->len )
+                 == 0 );
+
+    TEST_CF_SECRET( X, len * sizeof( mbedtls_mpi_uint ) );
+    TEST_CF_SECRET( Y, len * sizeof( mbedtls_mpi_uint ) );
+
+    ret = mbedtls_mpi_core_lt_ct( X, Y, len );
+
+    TEST_CF_PUBLIC( X, len * sizeof( mbedtls_mpi_uint ) );
+    TEST_CF_PUBLIC( Y, len * sizeof( mbedtls_mpi_uint ) );
+    TEST_CF_PUBLIC( &ret, sizeof( ret ) );
+
+    TEST_ASSERT( ret == exp_ret );
+
+exit:
+    ;
+
+    #undef MAX_LEN
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
 void mbedtls_mpi_lt_mpi_ct( int size_X, char * input_X,
                             int size_Y, char * input_Y,
                             int input_ret, int input_err )