diff --git a/core/vm/instructions.go b/core/vm/instructions.go
index 6b7b41220..2de35a443 100644
--- a/core/vm/instructions.go
+++ b/core/vm/instructions.go
@@ -341,19 +341,19 @@ func opCoinbase(instr instruction, env Environment, context *Context, memory *Me
 }
 
 func opTimestamp(instr instruction, env Environment, context *Context, memory *Memory, stack *stack) {
-	stack.push(new(big.Int).SetUint64(env.Time()))
+	stack.push(U256(new(big.Int).SetUint64(env.Time())))
 }
 
 func opNumber(instr instruction, env Environment, context *Context, memory *Memory, stack *stack) {
-	stack.push(U256(env.BlockNumber()))
+	stack.push(U256(new(big.Int).Set(env.BlockNumber())))
 }
 
 func opDifficulty(instr instruction, env Environment, context *Context, memory *Memory, stack *stack) {
-	stack.push(new(big.Int).Set(env.Difficulty()))
+	stack.push(U256(new(big.Int).Set(env.Difficulty())))
 }
 
 func opGasLimit(instr instruction, env Environment, context *Context, memory *Memory, stack *stack) {
-	stack.push(new(big.Int).Set(env.GasLimit()))
+	stack.push(U256(new(big.Int).Set(env.GasLimit())))
 }
 
 func opPop(instr instruction, env Environment, context *Context, memory *Memory, stack *stack) {
@@ -415,15 +415,12 @@ func opSstore(instr instruction, env Environment, context *Context, memory *Memo
 	env.State().SetState(context.Address(), loc, common.BigToHash(val))
 }
 
-func opJump(instr instruction, env Environment, context *Context, memory *Memory, stack *stack) {
-}
-func opJumpi(instr instruction, env Environment, context *Context, memory *Memory, stack *stack) {
-}
-func opJumpdest(instr instruction, env Environment, context *Context, memory *Memory, stack *stack) {
-}
+func opJump(instr instruction, env Environment, context *Context, memory *Memory, stack *stack)     {}
+func opJumpi(instr instruction, env Environment, context *Context, memory *Memory, stack *stack)    {}
+func opJumpdest(instr instruction, env Environment, context *Context, memory *Memory, stack *stack) {}
 
 func opPc(instr instruction, env Environment, context *Context, memory *Memory, stack *stack) {
-	stack.push(instr.data)
+	stack.push(new(big.Int).Set(instr.data))
 }
 
 func opMsize(instr instruction, env Environment, context *Context, memory *Memory, stack *stack) {
diff --git a/core/vm/jit.go b/core/vm/jit.go
index d5c2d7830..084d2a3f3 100644
--- a/core/vm/jit.go
+++ b/core/vm/jit.go
@@ -83,6 +83,7 @@ type Program struct {
 	code []byte
 }
 
+// NewProgram returns a new JIT program
 func NewProgram(code []byte) *Program {
 	program := &Program{
 		Id:           crypto.Sha3Hash(code),
@@ -113,6 +114,7 @@ func (p *Program) addInstr(op OpCode, pc uint64, fn instrFn, data *big.Int) {
 	p.mapping[pc] = len(p.instructions) - 1
 }
 
+// CompileProgram compiles the given program and return an error when it fails
 func CompileProgram(program *Program) (err error) {
 	if progStatus(atomic.LoadInt32(&program.status)) == progCompile {
 		return nil
@@ -272,6 +274,8 @@ func CompileProgram(program *Program) (err error) {
 	return nil
 }
 
+// RunProgram runs the program given the enviroment and context and returns an
+// error if the execution failed (non-consensus)
 func RunProgram(program *Program, env Environment, context *Context, input []byte) ([]byte, error) {
 	return runProgram(program, 0, NewMemory(), newstack(), env, context, input)
 }
@@ -352,6 +356,8 @@ func runProgram(program *Program, pcstart uint64, mem *Memory, stack *stack, env
 		pc++
 	}
 
+	context.Input = nil
+
 	return context.Return(nil), nil
 }