diff --git a/library/bignum_core.c b/library/bignum_core.c
index c9008a1d8..a23862bee 100644
--- a/library/bignum_core.c
+++ b/library/bignum_core.c
@@ -608,7 +608,11 @@ void mbedtls_mpi_core_montmul(mbedtls_mpi_uint *X,
      * So the correct return value is already in X if (carry ^ borrow) = 0,
      * but is in (the lower AN_limbs limbs of) T if (carry ^ borrow) = 1.
      */
-    mbedtls_ct_mpi_uint_cond_assign(AN_limbs, X, T, (unsigned char) (carry ^ borrow));
+    mbedtls_ct_memcpy_if(mbedtls_ct_bool(carry ^ borrow),
+                         (unsigned char *) X,
+                         (unsigned char *) T,
+                         NULL,
+                         AN_limbs * sizeof(mbedtls_mpi_uint));
 }
 
 int mbedtls_mpi_core_get_mont_r2_unsafe(mbedtls_mpi *X,
diff --git a/library/constant_time.c b/library/constant_time.c
index e9da8e0a9..c5255851e 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -295,36 +295,6 @@ unsigned mbedtls_ct_uint_if(unsigned condition,
     return (mask & if1) | (~mask & if0);
 }
 
-#if defined(MBEDTLS_BIGNUM_C)
-
-void mbedtls_ct_mpi_uint_cond_assign(size_t n,
-                                     mbedtls_mpi_uint *dest,
-                                     const mbedtls_mpi_uint *src,
-                                     unsigned char condition)
-{
-    size_t i;
-
-    /* MSVC has a warning about unary minus on unsigned integer types,
-     * but this is well-defined and precisely what we want to do here. */
-#if defined(_MSC_VER)
-#pragma warning( push )
-#pragma warning( disable : 4146 )
-#endif
-
-    /* all-bits 1 if condition is 1, all-bits 0 if condition is 0 */
-    const mbedtls_mpi_uint mask = -condition;
-
-#if defined(_MSC_VER)
-#pragma warning( pop )
-#endif
-
-    for (i = 0; i < n; i++) {
-        dest[i] = (src[i] & mask) | (dest[i] & ~mask);
-    }
-}
-
-#endif /* MBEDTLS_BIGNUM_C */
-
 #if defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT)
 
 void mbedtls_ct_memmove_left(void *start, size_t total, size_t offset)
diff --git a/library/constant_time_internal.h b/library/constant_time_internal.h
index 5e0d9c45f..f2cb4871b 100644
--- a/library/constant_time_internal.h
+++ b/library/constant_time_internal.h
@@ -147,27 +147,6 @@ unsigned mbedtls_ct_uint_if(unsigned condition,
                             unsigned if1,
                             unsigned if0);
 
-#if defined(MBEDTLS_BIGNUM_C)
-
-/** Conditionally assign a value without branches.
- *
- * This is equivalent to `if ( condition ) dest = src`, but is likely
- * to be compiled to code using bitwise operation rather than a branch.
- *
- * \param n             \p dest and \p src must be arrays of limbs of size n.
- * \param dest          The MPI to conditionally assign to. This must point
- *                      to an initialized MPI.
- * \param src           The MPI to be assigned from. This must point to an
- *                      initialized MPI.
- * \param condition     Condition to test, must be 0 or 1.
- */
-void mbedtls_ct_mpi_uint_cond_assign(size_t n,
-                                     mbedtls_mpi_uint *dest,
-                                     const mbedtls_mpi_uint *src,
-                                     unsigned char condition);
-
-#endif /* MBEDTLS_BIGNUM_C */
-
 #if defined(MBEDTLS_SSL_SOME_SUITES_USE_MAC)
 
 /** Conditional memcpy without branches.