diff --git a/library/bignum_core.c b/library/bignum_core.c
index 9adc4ef..7074a09 100644
--- a/library/bignum_core.c
+++ b/library/bignum_core.c
@@ -178,15 +178,14 @@
 }
 
 void mbedtls_mpi_core_cond_swap( mbedtls_mpi_uint *X,
-                                 size_t X_limbs,
                                  mbedtls_mpi_uint *Y,
-                                 size_t Y_limbs,
+                                 size_t limbs,
                                  unsigned char swap )
 {
     /* all-bits 1 if swap is 1, all-bits 0 if swap is 0 */
     mbedtls_mpi_uint limb_mask = mbedtls_ct_mpi_uint_mask( swap );
 
-    for( size_t i = 0; i < X_limbs; i++ )
+    for( size_t i = 0; i < limbs; i++ )
     {
         mbedtls_mpi_uint tmp = X[i];
         X[i] = ( X[i] & ~limb_mask ) | ( Y[i] & limb_mask );
diff --git a/library/bignum_core.h b/library/bignum_core.h
index a538ece..779fb08 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -123,9 +123,8 @@
  *                 values different to either of the original ones.
  */
 void mbedtls_mpi_core_cond_swap( mbedtls_mpi_uint *X,
-                                 size_t X_limbs,
                                  mbedtls_mpi_uint *Y,
-                                 size_t Y_limbs,
+                                 size_t limbs,
                                  unsigned char swap );
 
 /** Import X from unsigned binary data, little-endian.
diff --git a/library/bignum_mod_raw.c b/library/bignum_mod_raw.c
index 60ff9bb..bb4a37a 100644
--- a/library/bignum_mod_raw.c
+++ b/library/bignum_mod_raw.c
@@ -55,8 +55,7 @@
                                     const mbedtls_mpi_mod_modulus *m,
                                     unsigned char swap )
 {
-    mbedtls_mpi_core_cond_swap( X, m->limbs,
-                                Y, m->limbs, swap );
+    mbedtls_mpi_core_cond_swap( X, Y, m->limbs, swap );
 }
 
 int mbedtls_mpi_mod_raw_read( mbedtls_mpi_uint *X,
diff --git a/library/constant_time.c b/library/constant_time.c
index 09a86cd..7bf67f4 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -716,7 +716,7 @@
     X->s = mbedtls_ct_cond_select_sign( swap, Y->s, X->s );
     Y->s = mbedtls_ct_cond_select_sign( swap, s, Y->s );
 
-    mbedtls_mpi_core_cond_swap( X->p, X->n, Y->p, Y->n, swap );
+    mbedtls_mpi_core_cond_swap( X->p, Y->p, X->n, swap );
 
 cleanup:
     return( ret );