diff --git a/app/tools/gimptexttool-editor.c b/app/tools/gimptexttool-editor.c
index 5e2153f7bc..c84a5006ef 100644
--- a/app/tools/gimptexttool-editor.c
+++ b/app/tools/gimptexttool-editor.c
@@ -26,6 +26,7 @@
 #include <gtk/gtk.h>
 #include <gdk/gdkkeysyms.h>
 
+#include "libgimpbase/gimpbase.h"
 #include "libgimpwidgets/gimpwidgets.h"
 
 #include "tools-types.h"
@@ -1357,6 +1358,13 @@ gimp_text_tool_change_size (GimpTextTool *text_tool,
   GtkTextBuffer *buffer = GTK_TEXT_BUFFER (text_tool->buffer);
   GtkTextIter    start;
   GtkTextIter    end;
+  gdouble        default_size;
+  gdouble        x_res, y_res;
+
+  gimp_image_get_resolution (text_tool->image, &x_res, &y_res);
+
+  default_size = gimp_units_to_points (text_tool->text->font_size,
+                                       text_tool->text->unit, y_res);
 
   if (! gtk_text_buffer_get_selection_bounds (buffer, &start, &end))
     {
@@ -1365,7 +1373,7 @@ gimp_text_tool_change_size (GimpTextTool *text_tool,
 
   gtk_text_iter_order (&start, &end);
   gimp_text_buffer_change_size (text_tool->buffer, &start, &end,
-                                amount * PANGO_SCALE);
+                                amount * PANGO_SCALE, default_size * PANGO_SCALE);
 }
 
 static void
diff --git a/app/widgets/gimptextbuffer.c b/app/widgets/gimptextbuffer.c
index bfbeefe95b..ddd4a8f67e 100644
--- a/app/widgets/gimptextbuffer.c
+++ b/app/widgets/gimptextbuffer.c
@@ -442,7 +442,8 @@ void
 gimp_text_buffer_change_size (GimpTextBuffer    *buffer,
                               const GtkTextIter *start,
                               const GtkTextIter *end,
-                              gint               count)
+                              gint               count,
+                              gint               default_size)
 {
   GtkTextIter  iter;
   GtkTextIter  span_start;
@@ -479,16 +480,19 @@ gimp_text_buffer_change_size (GimpTextBuffer    *buffer,
       if (iter_size != span_size ||
           gtk_text_iter_compare (&iter, end) >= 0)
         {
+          gint base_size = (span_size == 0) ? default_size : span_size;
+          gint new_size  = base_size + count;
+
           if (span_size != 0)
             {
               gtk_text_buffer_remove_tag (GTK_TEXT_BUFFER (buffer), span_tag,
                                           &span_start, &span_end);
             }
 
-          if ((span_size + count) > 0)
+          if (new_size > 0)
             {
               span_tag = gimp_text_buffer_get_size_tag (buffer,
-                                                        span_size + count);
+                                                        new_size);
 
               gtk_text_buffer_apply_tag (GTK_TEXT_BUFFER (buffer), span_tag,
                                          &span_start, &span_end);
diff --git a/app/widgets/gimptextbuffer.h b/app/widgets/gimptextbuffer.h
index e3b818a36f..b5e64d0eb1 100644
--- a/app/widgets/gimptextbuffer.h
+++ b/app/widgets/gimptextbuffer.h
@@ -91,7 +91,8 @@ void             gimp_text_buffer_set_size             (GimpTextBuffer     *buff
 void             gimp_text_buffer_change_size          (GimpTextBuffer     *buffer,
                                                         const GtkTextIter  *start,
                                                         const GtkTextIter  *end,
-                                                        gint                amount);
+                                                        gint                amount,
+                                                        gint                default_size);
 
 GtkTextTag     * gimp_text_buffer_get_iter_baseline    (GimpTextBuffer     *buffer,
                                                         const GtkTextIter  *iter,