diff --git a/include/polarssl/bignum.h b/include/polarssl/bignum.h
index ce6ca86c0..da938021f 100644
--- a/include/polarssl/bignum.h
+++ b/include/polarssl/bignum.h
@@ -61,7 +61,7 @@
 
 /*
  * Maximum size of MPIs allowed in bits and bytes for user-MPIs.
- * ( Default: 512 bytes => 4096 bits )
+ * ( Default: 512 bytes => 4096 bits, Maximum: 1024 bytes => 8192 bits )
  *
  * Note: Calculations can results temporarily in larger MPIs. So the number
  * of limbs required (POLARSSL_MPI_MAX_LIMBS) is higher.