diff --git a/library/poly1305.c b/library/poly1305.c
index e22d3af..c22a0a1 100644
--- a/library/poly1305.c
+++ b/library/poly1305.c
@@ -49,6 +49,12 @@
 #define inline __inline
 #endif
 
+/* Parameter validation macros */
+#define POLY1305_VALIDATE_RET( cond )                                       \
+    MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA )
+#define POLY1305_VALIDATE( cond )                                           \
+    MBEDTLS_INTERNAL_VALIDATE( cond )
+
 #define POLY1305_BLOCK_SIZE_BYTES ( 16U )
 
 #define BYTES_TO_U32_LE( data, offset )                           \
@@ -276,27 +282,24 @@
 
 void mbedtls_poly1305_init( mbedtls_poly1305_context *ctx )
 {
-    if( ctx != NULL )
-    {
-        mbedtls_platform_zeroize( ctx, sizeof( mbedtls_poly1305_context ) );
-    }
+    POLY1305_VALIDATE( ctx != NULL );
+
+    mbedtls_platform_zeroize( ctx, sizeof( mbedtls_poly1305_context ) );
 }
 
 void mbedtls_poly1305_free( mbedtls_poly1305_context *ctx )
 {
     if( ctx != NULL )
-    {
-        mbedtls_platform_zeroize( ctx, sizeof( mbedtls_poly1305_context ) );
-    }
+        return;
+
+    mbedtls_platform_zeroize( ctx, sizeof( mbedtls_poly1305_context ) );
 }
 
 int mbedtls_poly1305_starts( mbedtls_poly1305_context *ctx,
                              const unsigned char key[32] )
 {
-    if( ctx == NULL || key == NULL )
-    {
-        return( MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
-    }
+    POLY1305_VALIDATE_RET( ctx != NULL );
+    POLY1305_VALIDATE_RET( key != NULL );
 
     /* r &= 0x0ffffffc0ffffffc0ffffffc0fffffff */
     ctx->r[0] = BYTES_TO_U32_LE( key, 0 )  & 0x0FFFFFFFU;
@@ -331,16 +334,8 @@
     size_t remaining = ilen;
     size_t queue_free_len;
     size_t nblocks;
-
-    if( ctx == NULL )
-    {
-        return( MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
-    }
-    else if( ( ilen > 0U ) && ( input == NULL ) )
-    {
-        /* input pointer is allowed to be NULL only if ilen == 0 */
-        return( MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
-    }
+    POLY1305_VALIDATE_RET( ctx != NULL );
+    POLY1305_VALIDATE_RET( ilen == 0 || input != NULL );
 
     if( ( remaining > 0U ) && ( ctx->queue_len > 0U ) )
     {
@@ -398,10 +393,8 @@
 int mbedtls_poly1305_finish( mbedtls_poly1305_context *ctx,
                              unsigned char mac[16] )
 {
-    if( ( ctx == NULL ) || ( mac == NULL ) )
-    {
-        return( MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
-    }
+    POLY1305_VALIDATE_RET( ctx != NULL );
+    POLY1305_VALIDATE_RET( mac != NULL );
 
     /* Process any leftover data */
     if( ctx->queue_len > 0U )
@@ -431,6 +424,9 @@
 {
     mbedtls_poly1305_context ctx;
     int ret;
+    POLY1305_VALIDATE_RET( key != NULL );
+    POLY1305_VALIDATE_RET( mac != NULL );
+    POLY1305_VALIDATE_RET( ilen == 0 || input != NULL );
 
     mbedtls_poly1305_init( &ctx );