diff --git a/include/ipmid/message/pack.hpp b/include/ipmid/message/pack.hpp
index 18863c4..deb0a5a 100644
--- a/include/ipmid/message/pack.hpp
+++ b/include/ipmid/message/pack.hpp
@@ -239,6 +239,10 @@
 {
     static int op(Payload& p, const std::vector<uint8_t>& t)
     {
+        if (p.bitCount != 0)
+        {
+            return 1;
+        }
         p.raw.reserve(p.raw.size() + t.size());
         p.raw.insert(p.raw.end(), t.begin(), t.end());
         return 0;
diff --git a/test/message/pack.cpp b/test/message/pack.cpp
index d0a738a..7e6cf31 100644
--- a/test/message/pack.cpp
+++ b/test/message/pack.cpp
@@ -235,6 +235,13 @@
     ASSERT_EQ(p.raw, k);
 }
 
+TEST(PackBasics, VectorUnaligned)
+{
+    ipmi::message::Payload p;
+    EXPECT_EQ(p.pack(true, std::vector<uint8_t>{1}), 1);
+    EXPECT_EQ(p.raw, std::vector<uint8_t>{0b1});
+}
+
 TEST(PackBasics, OptionalEmpty)
 {
     // an optional will only pack if the value is present