diff --git a/include/etl/span.h b/include/etl/span.h
index 8f57148f..5d03632a 100644
--- a/include/etl/span.h
+++ b/include/etl/span.h
@@ -1303,7 +1303,7 @@ namespace etl
   span<const byte, (Size == etl::dynamic_extent) ? (etl::dynamic_extent) : (Size * sizeof(T))> 
     as_bytes(span<T, Size> s) ETL_NOEXCEPT
   {
-    return span<const byte, (Size == etl::dynamic_extent) ? (etl::dynamic_extent) : (Size * sizeof(T))>(reinterpret_cast<byte*>(s.data()), s.size_bytes());
+    return span<const byte, (Size == etl::dynamic_extent) ? (etl::dynamic_extent) : (Size * sizeof(T))>(reinterpret_cast<const byte*>(s.data()), s.size_bytes());
   }
 
   //*************************************************************************
diff --git a/test/test_span_dynamic_extent.cpp b/test/test_span_dynamic_extent.cpp
index 7fc1c8c0..586eadcb 100644
--- a/test/test_span_dynamic_extent.cpp
+++ b/test/test_span_dynamic_extent.cpp
@@ -1325,8 +1325,9 @@ namespace
     TEST(test_convert_span_any_to_span_byte)
     {
       float data[2]{3.141592f, 2.71828f };
+      const float const_data[2]{3.141592f, 2.71828f };
 
-      auto const const_bytes    = etl::as_bytes(etl::span<float, etl::dynamic_extent>{data});
+      auto const const_bytes    = etl::as_bytes(etl::span<const float, etl::dynamic_extent>{const_data});
       auto const writable_bytes = etl::as_writable_bytes(etl::span<float, etl::dynamic_extent>{data});
 
       CHECK_EQUAL(const_bytes.size(),    sizeof(data));
diff --git a/test/test_span_fixed_extent.cpp b/test/test_span_fixed_extent.cpp
index 137bd9b8..a1825c2c 100644
--- a/test/test_span_fixed_extent.cpp
+++ b/test/test_span_fixed_extent.cpp
@@ -1163,12 +1163,13 @@ namespace
     TEST(test_convert_span_any_to_span_byte)
     {
       float data[2]{3.141592f, 2.71828f};
+      const float const_data[2]{3.141592f, 2.71828f};
 
 #if ETL_USING_CPP17
-      auto const const_bytes    = etl::as_bytes(etl::span{ data });
+      auto const const_bytes    = etl::as_bytes(etl::span{ const_data });
       auto const writable_bytes = etl::as_writable_bytes(etl::span{ data });
 #else
-      auto const const_bytes    = etl::as_bytes(etl::span<float, 2>(data));
+      auto const const_bytes    = etl::as_bytes(etl::span<const float, 2>(const_data));
       auto const writable_bytes = etl::as_writable_bytes(etl::span<float, 2>(data));
 #endif