diff --git a/opcode.go b/opcode.go
index bb32eeb94..2fcbd9fbd 100644
--- a/opcode.go
+++ b/opcode.go
@@ -840,7 +840,9 @@ func opcodeEndif(op *parsedOpcode, s *Script) error {
 		return StackErrNoIf
 	}
 
-	s.condStack = s.condStack[1:]
+	stk := make([]int, len(s.condStack) -1, len(s.condStack) -1)
+	copy(stk, s.condStack[1:])
+	s.condStack = stk
 	return nil
 }
 
diff --git a/stack.go b/stack.go
index 952d5bdb4..656c16a9e 100644
--- a/stack.go
+++ b/stack.go
@@ -173,7 +173,9 @@ func (s *Stack) nipN(idx int) (so []byte, err error) {
 	if idx == 0 {
 		s.stk = s.stk[:sz-1]
 	} else if idx == sz-1 {
-		s.stk = s.stk[1:]
+		s1 := make([][]byte, sz - 1, sz - 1)
+		copy(s1, s.stk[1:])
+		s.stk = s1
 	} else {
 		s1 := s.stk[sz-idx : sz]
 		s.stk = s.stk[:sz-idx-1]