diff --git a/library/bignum_core.c b/library/bignum_core.c
index 15557e67db..8e89766a72 100644
--- a/library/bignum_core.c
+++ b/library/bignum_core.c
@@ -38,7 +38,7 @@
 
 #include "bignum_core.h"
 
-size_t mbedtls_mpi_core_clz( const mbedtls_mpi_uint a )
+size_t mbedtls_mpi_core_clz( mbedtls_mpi_uint a )
 {
     size_t j;
     mbedtls_mpi_uint mask = (mbedtls_mpi_uint) 1 << (biL - 1);
diff --git a/library/bignum_core.h b/library/bignum_core.h
index 9fd9d2070e..434f52b5ee 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -37,7 +37,7 @@
  *
  * \return      The number of leading zero bits in \p a.
  */
-size_t mbedtls_mpi_core_clz( const mbedtls_mpi_uint a );
+size_t mbedtls_mpi_core_clz( mbedtls_mpi_uint a );
 
 /** Return the minimum number of bits required to represent the value held
  * in the MPI.