diff --git a/CMakeLists.txt b/CMakeLists.txt
index 96606e6..7159fa9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -16,14 +16,14 @@ option (MQTTSN_NO_WARN_AS_ERR "Don't treat compilation warnings as errors." OFF)
 #     is not provided and examples are not disabled.
 
 if ("${COMMSDSL_TAG}" STREQUAL "")
-    set(COMMSDSL_TAG "v3.5.1")
+    set(COMMSDSL_TAG "v3.5.2")
 endif ()
 
 if ("${COMMS_TAG}" STREQUAL "")
-    set(COMMS_TAG "v3.0.1")
+    set(COMMS_TAG "v3.1")
 endif ()
 
-set (VERSION "0.18.1")
+set (VERSION "0.19")
 
 set (EXTERNALS_DIR "${PROJECT_SOURCE_DIR}/externals")
 
@@ -55,7 +55,7 @@ if ("${COMMSDSL2COMMS}" STREQUAL "")
                 -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE} -DCMAKE_INSTALL_PREFIX=${commsdsl2comms_install_dir}
                 -DCOMMSDSL_NO_TESTS=ON -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER} 
                 -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} -DBOOST_ROOT=${BOOST_ROOT}
-                ${boost_static_libs_param}
+                -DCOMMSDSL_EXTERNALS_DIR=${EXTERNALS_DIR} ${boost_static_libs_param}
             BINARY_DIR "${commsdsl2comms_bin_dir}"
         )
         
diff --git a/src/include/mqttsn/field/MsgLengthField.h.public b/src/include/mqttsn/field/MsgLengthField.h.public
index 6fda4e2..1139107 100644
--- a/src/include/mqttsn/field/MsgLengthField.h.public
+++ b/src/include/mqttsn/field/MsgLengthField.h.public
@@ -22,3 +22,10 @@ void setLengthValue(std::size_t val)
     field_long().setExists();
     field_long().field().value() = static_cast<std::uint16_t>(val);
 }
+
+// Verifying compile time length calculations.
+static constexpr std::size_t MinLen = Base::minLength();
+static constexpr std::size_t MaxLen = Base::maxLength();
+static_assert(MinLen == Field_short::minLength(), "Invalid length assumption");
+static_assert(MaxLen == (Field_short::maxLength() + Field_long::Field::maxLength()), 
+    "Invalid length assumption");
\ No newline at end of file