[plt-scheme] scheme_make_hash_table

I expected this code to declare a hash table, then insert 2 values in it. 
Instead it looks like 1 value is inserted, and it's the wrong one.

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#include "scheme.h"

int main(int argc, char ** args)
{
  Scheme_Env * env = scheme_basic_env();
  Scheme_Hash_Table * hash = scheme_make_hash_table(SCHEME_hash_string);
  scheme_add_global("*hash*", (Scheme_Object *)hash, env);

  scheme_eval_string(
		     "(hash-table-put! *hash* \"a\" 1)"
		     "(hash-table-put! *hash* \"b\" 2)"
		     , env);

  printf("count: %d\n", hash->count);
  for (int i=0; i<hash->size; i++){
    if (hash->vals[i])
      printf("key: %s, val: %d\n", hash->keys[i], hash->vals[i]);
  }
  return 0;
}

-------------------------------
prints:
count: 1
key: *, val: 3

What am I missing?

Wayne