diff --git a/src/libslic3r/Fill/FillBase.cpp b/src/libslic3r/Fill/FillBase.cpp
index a8d5d20e2..b38c5c9f8 100644
--- a/src/libslic3r/Fill/FillBase.cpp
+++ b/src/libslic3r/Fill/FillBase.cpp
@@ -21,6 +21,8 @@
 #include "FillAdaptive.hpp"
 #include "FillLightning.hpp"
 
+#include <boost/log/trivial.hpp>
+
 // #define INFILL_DEBUG_OUTPUT
 
 namespace Slic3r {
@@ -129,8 +131,8 @@ std::pair<float, Point> Fill::_infill_direction(const Surface *surface) const
     float out_angle = this->angle;
 
 	if (out_angle == FLT_MAX) {
-		//FIXME Vojtech: Add a warning?
-        printf("Using undefined infill angle\n");
+        assert(false);
+        BOOST_LOG_TRIVIAL(error) << "Using undefined infill angle";
         out_angle = 0.f;
     }