PVS-Studio warning V220 for OpenSSL

void *CRYPTO_malloc(int num, const char *file, int line);

#define OPENSSL_malloc(num) \
  CRYPTO_malloc((int)num,__FILE__,__LINE__)

int ec_GFp_simple_points_make_affine(....)
{
  BIGNUM **heap = NULL;
  size_t pow2 = 0;
  ....
  heap = OPENSSL_malloc(pow2 * sizeof heap[0]);
  ....
}

This suspicious code was found in OpenSSL project by PVS-Studio static code analyzer.
Warning message is:
V220 Suspicious sequence of types castings: memsize -> 32-bit integer -> memsize. The value being casted: 'pow2'. ecp_smpl.c 1576

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/