diff --git a/FL/Fl_Text_Display.H b/FL/Fl_Text_Display.H
index 8f83bb7ad..2e9a0a0d9 100644
--- a/FL/Fl_Text_Display.H
+++ b/FL/Fl_Text_Display.H
@@ -250,7 +250,7 @@ class FL_EXPORT Fl_Text_Display: public Fl_Group {
                                int *retLineStart, int *retLineEnd,
                                bool countLastLineMissingNewLine = true) const;
     void find_line_end(int pos, bool start_pos_is_line_start, int *lineEnd,
-                         int *nextLineStart);
+                         int *nextLineStart) const;
     int measure_proportional_character(char c, int colNum, int pos) const;
     int wrap_uses_character(int lineEndPos) const;
     int range_touches_selection(const Fl_Text_Selection *sel, int rangeStart,
diff --git a/src/Fl_Text_Display.cxx b/src/Fl_Text_Display.cxx
index 521048685..77bc70254 100644
--- a/src/Fl_Text_Display.cxx
+++ b/src/Fl_Text_Display.cxx
@@ -2963,7 +2963,7 @@ int Fl_Text_Display::measure_proportional_character(char c, int colNum, int pos)
    the way back to the beginning of the line.
 */
 void Fl_Text_Display::find_line_end(int startPos, bool startPosIsLineStart,
-    	int *lineEnd, int *nextLineStart) {
+    	int *lineEnd, int *nextLineStart) const {
     int retLines, retLineStart;
     
     /* if we're not wrapping use more efficient BufEndOfLine */