diff --git a/include/bit_vector.hpp b/include/bit_vector.hpp
index ba0fb57..9cd515f 100644
--- a/include/bit_vector.hpp
+++ b/include/bit_vector.hpp
@@ -97,6 +97,7 @@ struct bit_vector  //
 
         void append_bits(uint64_t bits, uint64_t len) {
             // check there are no spurious bits
+            assert(len <= 64);
             assert(len == 64 || (bits >> len) == 0);
             if (!len) return;
             uint64_t pos_in_word = m_num_bits & 63;
diff --git a/include/compact_vector.hpp b/include/compact_vector.hpp
index 59c1753..75db609 100644
--- a/include/compact_vector.hpp
+++ b/include/compact_vector.hpp
@@ -2,6 +2,7 @@
 
 #include <vector>
 #include <cmath>
+#include <cstring>
 #include <iterator>
 
 #include "essentials.hpp"
@@ -253,7 +254,9 @@ struct compact_vector  //
         assert(i < size());
         uint64_t pos = i * m_width;
         const char* ptr = reinterpret_cast<const char*>(m_data.data());
-        return (*(reinterpret_cast<uint64_t const*>(ptr + (pos >> 3))) >> (pos & 7)) & m_mask;
+        uint64_t word;
+        std::memcpy(&word, ptr + (pos >> 3), sizeof(uint64_t));
+        return (word >> (pos & 7)) & m_mask;
     }
 
     uint64_t back() const { return operator[](size() - 1); }