diff --git a/library/poly1305.c b/library/poly1305.c
index a30b170..3c0b7c6 100644
--- a/library/poly1305.c
+++ b/library/poly1305.c
@@ -122,10 +122,10 @@
     for( i = 0U; i < nblocks; i++ )
     {
         /* The input block is treated as a 128-bit little-endian integer */
-        d0   = BYTES_TO_U32_LE( input, offset + 0  );
-        d1   = BYTES_TO_U32_LE( input, offset + 4  );
-        d2   = BYTES_TO_U32_LE( input, offset + 8  );
-        d3   = BYTES_TO_U32_LE( input, offset + 12 );
+        d0   = MBEDTLS_BYTES_TO_U32_LE( input, offset + 0  );
+        d1   = MBEDTLS_BYTES_TO_U32_LE( input, offset + 4  );
+        d2   = MBEDTLS_BYTES_TO_U32_LE( input, offset + 8  );
+        d3   = MBEDTLS_BYTES_TO_U32_LE( input, offset + 12 );
 
         /* Compute: acc += (padded) block as a 130-bit integer */
         d0  += (uint64_t) acc0;
@@ -290,15 +290,15 @@
     POLY1305_VALIDATE_RET( key != NULL );
 
     /* r &= 0x0ffffffc0ffffffc0ffffffc0fffffff */
-    ctx->r[0] = BYTES_TO_U32_LE( key, 0 )  & 0x0FFFFFFFU;
-    ctx->r[1] = BYTES_TO_U32_LE( key, 4 )  & 0x0FFFFFFCU;
-    ctx->r[2] = BYTES_TO_U32_LE( key, 8 )  & 0x0FFFFFFCU;
-    ctx->r[3] = BYTES_TO_U32_LE( key, 12 ) & 0x0FFFFFFCU;
+    ctx->r[0] = MBEDTLS_BYTES_TO_U32_LE( key, 0 )  & 0x0FFFFFFFU;
+    ctx->r[1] = MBEDTLS_BYTES_TO_U32_LE( key, 4 )  & 0x0FFFFFFCU;
+    ctx->r[2] = MBEDTLS_BYTES_TO_U32_LE( key, 8 )  & 0x0FFFFFFCU;
+    ctx->r[3] = MBEDTLS_BYTES_TO_U32_LE( key, 12 ) & 0x0FFFFFFCU;
 
-    ctx->s[0] = BYTES_TO_U32_LE( key, 16 );
-    ctx->s[1] = BYTES_TO_U32_LE( key, 20 );
-    ctx->s[2] = BYTES_TO_U32_LE( key, 24 );
-    ctx->s[3] = BYTES_TO_U32_LE( key, 28 );
+    ctx->s[0] = MBEDTLS_BYTES_TO_U32_LE( key, 16 );
+    ctx->s[1] = MBEDTLS_BYTES_TO_U32_LE( key, 20 );
+    ctx->s[2] = MBEDTLS_BYTES_TO_U32_LE( key, 24 );
+    ctx->s[3] = MBEDTLS_BYTES_TO_U32_LE( key, 28 );
 
     /* Initial accumulator state */
     ctx->acc[0] = 0U;