diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index 85812f5080..be4c056d79 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -607,10 +607,10 @@ mbedtls_mpi_core_lt_ct: x=y (0 limbs)
 mpi_core_lt_ct:"":"":0
 
 mbedtls_mpi_core_lt_ct: x>y (63 bit x, y first byte greater)
-mpi_core_lt_ct:"7FFFFFFFFFFFFFFF":"FF":0
+mpi_core_lt_ct:"7FFFFFFFFFFFFFFF":"00000000000000FF":0
 
 mbedtls_mpi_core_lt_ct: x<y (63 bit y, x first byte greater)
-mpi_core_lt_ct:"FF":"7FFFFFFFFFFFFFFF":1
+mpi_core_lt_ct:"00000000000000FF":"7FFFFFFFFFFFFFFF":1
 
 mbedtls_mpi_core_lt_ct: x>y (64 bit x, y=x-1)
 mpi_core_lt_ct:"8000000000000000":"7FFFFFFFFFFFFFFF":0
@@ -619,28 +619,28 @@ mbedtls_mpi_core_lt_ct: x<y (64 bit y, x=y-1)
 mpi_core_lt_ct:"7FFFFFFFFFFFFFFF":"8000000000000000":1
 
 mbedtls_mpi_core_lt_ct: x>y (64 bit x, y=1)
-mpi_core_lt_ct:"8000000000000000":"01":0
+mpi_core_lt_ct:"8000000000000000":"0000000000000001":0
 
 mbedtls_mpi_core_lt_ct: x<y (64 bit y, x=1)
-mpi_core_lt_ct:"01":"8000000000000000":1
+mpi_core_lt_ct:"0000000000000001":"8000000000000000":1
 
 mbedtls_mpi_core_lt_ct: x>y (64 bit x, y=0)
-mpi_core_lt_ct:"8000000000000000":"00":0
+mpi_core_lt_ct:"8000000000000000":"0000000000000000":0
 
 mbedtls_mpi_core_lt_ct: x<y (64 bit y, x=0)
-mpi_core_lt_ct:"00":"8000000000000000":1
+mpi_core_lt_ct:"0000000000000000":"8000000000000000":1
 
 mbedtls_mpi_core_lt_ct: x>y (64 bit x, first bytes equal)
-mpi_core_lt_ct:"FFFFFFFFFFFFFFFF":"FF":0
+mpi_core_lt_ct:"FFFFFFFFFFFFFFFF":"00000000000000FF":0
 
 mbedtls_mpi_core_lt_ct: x<y (64 bit y, first bytes equal)
-mpi_core_lt_ct:"FF":"FFFFFFFFFFFFFFFF":1
+mpi_core_lt_ct:"00000000000000FF":"FFFFFFFFFFFFFFFF":1
 
 mbedtls_mpi_core_lt_ct: x>y (31 bit x, y first byte greater)
-mpi_core_lt_ct:"7FFFFFFF":"FF":0
+mpi_core_lt_ct:"7FFFFFFF":"000000FF":0
 
 mbedtls_mpi_core_lt_ct: x<y (31 bit y, x first byte greater)
-mpi_core_lt_ct:"FF":"7FFFFFFF":1
+mpi_core_lt_ct:"000000FF":"7FFFFFFF":1
 
 mbedtls_mpi_core_lt_ct: x>y (32 bit x, y=x-1)
 mpi_core_lt_ct:"80000000":"7FFFFFFF":0
@@ -649,22 +649,22 @@ mbedtls_mpi_core_lt_ct: x<y (32 bit y, x=y-1)
 mpi_core_lt_ct:"7FFFFFFF":"80000000":1
 
 mbedtls_mpi_core_lt_ct: x>y (32 bit x, y=1)
-mpi_core_lt_ct:"80000000":"01":0
+mpi_core_lt_ct:"80000000":"00000001":0
 
 mbedtls_mpi_core_lt_ct: x<y (32 bit y, x=1)
-mpi_core_lt_ct:"01":"80000000":1
+mpi_core_lt_ct:"00000001":"80000000":1
 
 mbedtls_mpi_core_lt_ct: x>y (32 bit x, y=0)
-mpi_core_lt_ct:"80000000":"00":0
+mpi_core_lt_ct:"80000000":"00000000":0
 
 mbedtls_mpi_core_lt_ct: x<y (32 bit y, x=0)
-mpi_core_lt_ct:"00":"80000000":1
+mpi_core_lt_ct:"00000000":"80000000":1
 
 mbedtls_mpi_core_lt_ct: x>y (32 bit x, first bytes equal)
-mpi_core_lt_ct:"FFFFFFFF":"FF":0
+mpi_core_lt_ct:"FFFFFFFF":"000000FF":0
 
 mbedtls_mpi_core_lt_ct: x<y (32 bit y, first bytes equal)
-mpi_core_lt_ct:"FF":"FFFFFFFF":1
+mpi_core_lt_ct:"000000FF":"FFFFFFFF":1
 
 mbedtls_mpi_core_lt_ct: x<y, zero vs non-zero MS limb
 mpi_core_lt_ct:"00FFFFFFFFFFFFFFFF":"01FFFFFFFFFFFFFFFF":1
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index ff2eaac4ba..d4501972de 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -728,38 +728,29 @@ exit:
 /* END_CASE */
 
 /* BEGIN_CASE */
-void mpi_core_lt_ct( data_t * input_X, data_t * input_Y, int input_ret )
+void mpi_core_lt_ct( data_t * input_X, data_t * input_Y, int exp_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 );
+    mbedtls_mpi_uint *X = NULL;
+    size_t X_limbs;
+    mbedtls_mpi_uint *Y = NULL;
+    size_t Y_limbs;
+    int ret;
 
-    TEST_LE_U( len, MAX_LEN );
+    TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &X, &X_limbs, input_X ) );
+    TEST_EQUAL( 0, mbedtls_test_read_mpi_core( &Y, &Y_limbs, input_Y ) );
 
-    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 );
+    /* We need two same-length limb arrays */
+    TEST_EQUAL( X_limbs, Y_limbs );
 
-    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_CF_SECRET( X, X_limbs * sizeof( mbedtls_mpi_uint ) );
+    TEST_CF_SECRET( Y, X_limbs * sizeof( mbedtls_mpi_uint ) );
 
+    ret = mbedtls_mpi_core_lt_ct( X, Y, X_limbs );
     TEST_EQUAL( ret, exp_ret );
 
 exit:
-    ;
-
-    #undef MAX_LEN
+    mbedtls_free( X );
+    mbedtls_free( Y );
 }
 /* END_CASE */