diff --git a/gr-fec/include/gnuradio/fec/polar_decoder_common.h b/gr-fec/include/gnuradio/fec/polar_decoder_common.h
index b0ecb85..d738ae4 100644
--- a/gr-fec/include/gnuradio/fec/polar_decoder_common.h
+++ b/gr-fec/include/gnuradio/fec/polar_decoder_common.h
@@ -64,7 +64,11 @@ namespace gr {
         bool set_frame_size(unsigned int frame_size){return false;};
 
       private:
+#ifdef BOOST_NO_CXX11_CONSTEXPR
         static const float D_LLR_FACTOR = -2.19722458f;
+#else
+        static constexpr float D_LLR_FACTOR = -2.19722458f;
+#endif
         unsigned int d_frozen_bit_counter;
 
       protected: