diff --git a/include/boost/gil/channel.hpp b/include/boost/gil/channel.hpp
index d073a3761..84ed48bf8 100644
--- a/include/boost/gil/channel.hpp
+++ b/include/boost/gil/channel.hpp
@@ -344,7 +344,7 @@ protected:
     static const num_value_t num_values = static_cast< num_value_t >( 1 ) << NumBits ;
     static const max_value_t max_val    = static_cast< max_value_t >( num_values - 1 );
     
-#ifdef GIL_NONWORD_POINTER_ALIGNMENT_SUPPORTED
+#if defined(BOOST_GIL_CONFIG_HAS_UNALIGNED_ACCESS)
     const bitfield_t& get_data()                      const { return *static_cast<const bitfield_t*>(_data_ptr); }
     void              set_data(const bitfield_t& val) const {        *static_cast<      bitfield_t*>(_data_ptr) = val; }
 #else
diff --git a/include/boost/gil/gil_config.hpp b/include/boost/gil/gil_config.hpp
index a005e8a26..70fa1eeb0 100644
--- a/include/boost/gil/gil_config.hpp
+++ b/include/boost/gil/gil_config.hpp
@@ -1,6 +1,7 @@
 /*
     Copyright 2005-2007 Adobe Systems Incorporated
-   
+    Copyright 2018 Mateusz Loskot <mateusz at loskot dot net>
+
     Use, modification and distribution are subject to the Boost Software License,
     Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
     http://www.boost.org/LICENSE_1_0.txt).
@@ -14,7 +15,7 @@
 #define GIL_CONFIG_HPP
 
 ////////////////////////////////////////////////////////////////////////////////////////
-/// \file               
+/// \file
 /// \brief GIL configuration file
 /// \author Lubomir Bourdev and Hailin Jin \n
 ///         Adobe Systems Incorporated
@@ -22,13 +23,40 @@
 ////////////////////////////////////////////////////////////////////////////////////////
 
 #include <boost/config.hpp>
+#include <boost/config/pragma_message.hpp>
 
 #define GIL_VERSION "2.1.2"
 
-// Enable GIL_NONWORD_POINTER_ALIGNMENT_SUPPORTED if your platform supports dereferencing on non-word memory boundary.
-// Enabling the flag results in performance improvement
-#if !defined(__hpux) && !defined(sun) && !defined(__sun) && !defined(__osf__)
-    #define GIL_NONWORD_POINTER_ALIGNMENT_SUPPORTED
+#if defined(BOOST_GIL_DOXYGEN_ONLY)
+/// \def BOOST_GIL_CONFIG_HAS_UNALIGNED_ACCESS
+/// \brief Define to allow unaligned memory access
+/// Theoretically (or historically?) on platforms which support dereferencing on
+/// non-word memory boundary, unaligned access may result in performance improvement.
+/// \warning Unfortunately, this optimization may be a C/C++ strict aliasing rules
+/// violation, if accessed data buffer has effective type that cannot be aliased
+/// without leading to undefined behaviour.
+#define BOOST_GIL_CONFIG_HAS_UNALIGNED_ACCESS
 #endif
 
+#if defined(BOOST_GIL_CONFIG_HAS_UNALIGNED_ACCESS)
+#if defined(sun) || defined(__sun) || \             // SunOS
+    defined(__osf__) || defined(__osf) || \         // Tru64
+    defined(_hpux) || defined(hpux) || \            // HP-UX
+    defined(__arm__) || defined(__ARM_ARCH) || \    // ARM
+    defined(_AIX)                                   // AIX
+#error Unaligned access strictly disabled for some UNIX platforms or ARM architecture
+#elif defined(__i386__) || defined(__x86_64__) || defined(__vax__)
+    // The check for little-endian architectures that tolerate unaligned memory
+    // accesses is just an optimization. Nothing will break if it fails to detect
+    // a suitable architecture.
+    //
+    // Unfortunately, this optimization may be a C/C++ strict aliasing rules violation
+    // if accessed data buffer has effective type that cannot be aliased
+    // without leading to undefined behaviour.
+BOOST_PRAGMA_MESSAGE("CAUTION: Unaligned access tolerated on little-endian may cause undefined behaviour")
+#else
+#error Unaligned access disabled for unknown platforms and architectures
+#endif
+#endif // defined(BOOST_GIL_CONFIG_HAS_UNALIGNED_ACCESS)
+
 #endif