diff --git a/libuavcan/include/uavcan/impl_constants.hpp b/libuavcan/include/uavcan/impl_constants.hpp
index 726691a32f..0504628812 100644
--- a/libuavcan/include/uavcan/impl_constants.hpp
+++ b/libuavcan/include/uavcan/impl_constants.hpp
@@ -108,8 +108,13 @@ namespace uavcan
  * fit this size; otherwise compilation fails.
  */
 #if UAVCAN_MEM_POOL_BLOCK_SIZE
+/// Explicitly specified by the user.
 static const unsigned MemPoolBlockSize = UAVCAN_MEM_POOL_BLOCK_SIZE;
+#elif defined(__BIGGEST_ALIGNMENT__) && (__BIGGEST_ALIGNMENT__ <= 8)
+/// Convenient default for GCC-like compilers - if alignment allows, pool block size can be safely reduced.
+static const unsigned MemPoolBlockSize = 56;
 #else
+/// Safe default that should be OK for any platform.
 static const unsigned MemPoolBlockSize = 64;
 #endif