diff --git a/src/libslic3r/GCodeWriter.cpp b/src/libslic3r/GCodeWriter.cpp
index 9388738775..0b78ce96ae 100644
--- a/src/libslic3r/GCodeWriter.cpp
+++ b/src/libslic3r/GCodeWriter.cpp
@@ -741,9 +741,9 @@ std::string GCodeWriter::set_fan(const GCodeFlavor gcode_flavor, unsigned int sp
             gcode << "M126";    break;
         case gcfMach3:
         case gcfMachinekit:
-            gcode << "M106 P" << 255.0 * speed / 100.0; break;
+            gcode << "M106 P" << static_cast<unsigned int>(255.5 * speed / 100.0); break;
         default:
-            gcode << "M106 S" << 255.0 * speed / 100.0; break;
+            gcode << "M106 S" << static_cast<unsigned int>(255.5 * speed / 100.0); break;
         }
         if (GCodeWriter::full_gcode_comment) 
             gcode << " ; enable fan";