diff --git a/include/fc/variant.hpp b/include/fc/variant.hpp
index 7cdc96c..3e7b095 100644
--- a/include/fc/variant.hpp
+++ b/include/fc/variant.hpp
@@ -213,8 +213,7 @@ namespace fc
         template<typename T>
         variant& operator=( T&& v )
         {
-           *this = variant( fc::forward<T>(v) );
-           return *this;
+           return *this = variant( fc::forward<T>(v) );
         }
 
         template<typename T>
diff --git a/src/crypto/bigint.cpp b/src/crypto/bigint.cpp
index d13675e..0682992 100644
--- a/src/crypto/bigint.cpp
+++ b/src/crypto/bigint.cpp
@@ -4,12 +4,16 @@
 #include <fc/variant.hpp>
 #include <fc/crypto/base64.hpp>
 
+#include <fc/exception/exception.hpp>
+
 namespace fc {
       bigint::bigint( const char* bige, uint32_t l ) {
         n = BN_bin2bn( (const unsigned char*)bige, l, NULL );
+        FC_ASSERT( n != nullptr );
       }
       bigint::bigint( const std::vector<char>& bige ) {
         n = BN_bin2bn( (const unsigned char*)bige.data(), bige.size(), NULL );
+        FC_ASSERT( n != nullptr );
       }
       bigint::bigint( BIGNUM* in )
       {
@@ -151,6 +155,8 @@ namespace fc {
       bigint& bigint::operator <<= ( uint32_t i )
       {
          bigint tmp;
+         FC_ASSERT( tmp.n != nullptr );
+         FC_ASSERT( n != nullptr );
          BN_lshift( tmp.n, n, i );
          std::swap(*this,tmp);
          return *this;
diff --git a/src/io/json.cpp b/src/io/json.cpp
index d9028a4..c8d96ba 100644
--- a/src/io/json.cpp
+++ b/src/io/json.cpp
@@ -298,7 +298,9 @@ namespace fc
             case 0x04: // ^D end of transmission
               FC_THROW_EXCEPTION( eof_exception, "unexpected end of file" );
             default:
+              in.get(); // 
               ilog( "unhandled char '${c}' int ${int}", ("c", fc::string( &c, 1 ) )("int", int(c)) );
+              return variant();
          }
       }
 	  return variant();
diff --git a/src/variant.cpp b/src/variant.cpp
index 86ee07d..d4c69ad 100644
--- a/src/variant.cpp
+++ b/src/variant.cpp
@@ -166,7 +166,7 @@ void variant::clear()
      default:
         break;
    }
-   memset( this, 0, sizeof(*this) );
+   set_variant_type( this, null_type );
 }
 
 variant::variant( const variant& v )
@@ -207,8 +207,9 @@ variant::~variant()
 variant& variant::operator=( variant&& v )
 {
    if( this == &v ) return *this;
+   clear();
    memcpy( (char*)this, (char*)&v, sizeof(v) );
-   v.clear();
+   set_variant_type( &v, null_type ); 
    return *this;
 }