diff --git a/src/libslic3r/GCode/GCodeProcessor.cpp b/src/libslic3r/GCode/GCodeProcessor.cpp
index cfdcf6d1e..f85088b08 100644
--- a/src/libslic3r/GCode/GCodeProcessor.cpp
+++ b/src/libslic3r/GCode/GCodeProcessor.cpp
@@ -3721,8 +3721,13 @@ void GCodeProcessor::post_process()
     }
 
     auto process_used_filament = [&](std::string& gcode_line) {
-        auto process_tag = [](std::string& gcode_line, const std::string& tag, const std::vector<double>& values) {
-            if (boost::algorithm::istarts_with(gcode_line, tag)) {
+        // Prefilter for parsing speed.
+        if (gcode_line.size() < 8 || gcode_line[0] != ';' || gcode_line[1] != ' ')
+            return false;
+        if (const char c = gcode_line[2]; c != 'f' && c != 't')
+            return false;
+        auto process_tag = [](std::string& gcode_line, const std::string_view tag, const std::vector<double>& values) {
+            if (boost::algorithm::starts_with(gcode_line, tag)) {
                 gcode_line = tag;
                 char buf[1024];
                 for (size_t i = 0; i < values.size(); ++i) {
diff --git a/src/slic3r/GUI/ImGuiWrapper.cpp b/src/slic3r/GUI/ImGuiWrapper.cpp
index 5ab4685bf..7345c73b4 100644
--- a/src/slic3r/GUI/ImGuiWrapper.cpp
+++ b/src/slic3r/GUI/ImGuiWrapper.cpp
@@ -544,7 +544,7 @@ bool ImGuiWrapper::slider_float(const char* label, float* v, float v_min, float
     const float max_tooltip_width = ImGui::GetFontSize() * 20.0f;
 
     // let the label string start with "##" to hide the automatic label from ImGui::SliderFloat()
-    bool label_visible = !boost::algorithm::istarts_with(label, "##");
+    bool label_visible = !boost::algorithm::starts_with(label, "##");
     std::string str_label = label_visible ? std::string("##") + std::string(label) : std::string(label);
 
     // removes 2nd evenience of "##", if present