diff --git a/library/constant_time_internal.h b/library/constant_time_internal.h
index 61a5c6d..26f6606 100644
--- a/library/constant_time_internal.h
+++ b/library/constant_time_internal.h
@@ -433,7 +433,7 @@
  * Block memory operations
  */
 
-#if defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT)
+#if defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C)
 
 /** Conditionally set a block of memory to zero.
  *
@@ -466,7 +466,7 @@
                              size_t total,
                              size_t offset);
 
-#endif /* defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT) */
+#endif /* defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) */
 
 /** Conditional memcpy.
  *