Index: firmware/export/font.h
===================================================================
--- firmware/export/font.h	(revision 30753)
+++ firmware/export/font.h	(working copy)
@@ -118,6 +118,7 @@
 const char* font_filename(int font_id);
 int font_load(const char *path);
 int font_load_ex(const char *path, size_t buffer_size);
+void font_lock( int font_id, bool lock);
 int font_glyphs_to_bufsize(const char *path, int glyphs);
 void font_unload(int font_id);
 
Index: firmware/font.c
===================================================================
--- firmware/font.c	(revision 30753)
+++ firmware/font.c	(working copy)
@@ -117,6 +117,14 @@
         alloc->handle_locks--;
 }
 
+void font_lock(int font_id, bool lock)
+{
+    if( font_id == FONT_SYSFIXED )
+        return;
+    if( buflib_allocations[font_id] != -1 )
+        lock_font_handle(buflib_allocations[font_id], lock);
+}
+
 static struct buflib_callbacks buflibops = {buflibmove_callback, NULL };
 
 static inline struct font *pf_from_handle(int handle)
@@ -919,7 +927,8 @@
     struct font* pf = font_get(fontnumber);
     unsigned short ch;
     int width = 0;
-
+    
+    font_lock( fontnumber, true );
     for (str = utf8decode(str, &ch); ch != 0 ; str = utf8decode(str, &ch))
     {
         if (is_diacritic(ch, NULL))
@@ -932,6 +941,7 @@
         *w = width;
     if ( h )
         *h = pf->height;
+    font_lock( fontnumber, false );
     return width;
 }
 
Index: firmware/drivers/lcd-bitmap-common.c
===================================================================
--- firmware/drivers/lcd-bitmap-common.c	(revision 30753)
+++ firmware/drivers/lcd-bitmap-common.c	(working copy)
@@ -101,6 +101,7 @@
 static void LCDFN(putsxyofs)(int x, int y, int ofs, const unsigned char *str)
 {
     unsigned short *ucs;
+    font_lock(current_vp->font, true);
     struct font* pf = font_get(current_vp->font);
     int vp_flags = current_vp->flags;
     int rtl_next_non_diac_width, last_non_diacritic_width;
@@ -233,6 +234,7 @@
             }
         }
     }
+    font_lock(current_vp->font, false);
 }
 
 /* put a string at a given pixel position */
@@ -457,6 +459,7 @@
         else
             s->offset += LCDFN(scroll_info).step;
 
+        font_lock(current_vp->font, true);
         pf = font_get(current_vp->font);
         xpos = s->startx;
         ypos = s->y * pf->height + s->y_offset;
@@ -492,6 +495,7 @@
                                pf->height, s->offset);
         LCDFN(update_viewport_rect)(xpos, ypos, current_vp->width - xpos,
                                pf->height);
+        font_lock(current_vp->font, false);
     }
     LCDFN(set_viewport)(old_vp);
 }