diff --git a/defs.h b/defs.h
index b8205c10..e5d3fefe 100644
--- a/defs.h
+++ b/defs.h
@@ -170,6 +170,8 @@ typedef struct SessionSpecial SessionSpecial;
 
 typedef struct StripCtrlChars StripCtrlChars;
 
+typedef struct BidiContext BidiContext;
+
 /*
  * A small structure wrapping up a (pointer, length) pair so that it
  * can be conveniently passed to or from a function.
diff --git a/putty.h b/putty.h
index 334b588b..6bff90bb 100644
--- a/putty.h
+++ b/putty.h
@@ -2359,7 +2359,9 @@ typedef struct bidi_char {
     unsigned int origwc, wc;
     unsigned short index, nchars;
 } bidi_char;
-int do_bidi(bidi_char *line, int count);
+BidiContext *bidi_new_context(void);
+void bidi_free_context(BidiContext *ctx);
+void do_bidi(BidiContext *ctx, bidi_char *line, size_t count);
 int do_shape(bidi_char *line, bidi_char *to, int count);
 bool is_rtl(int c);
 
diff --git a/terminal/bidi.c b/terminal/bidi.c
index 4c55b86e..15ed23d0 100644
--- a/terminal/bidi.c
+++ b/terminal/bidi.c
@@ -1116,6 +1116,22 @@ int do_shape(bidi_char *line, bidi_char *to, int count)
     return 1;
 }
 
+struct BidiContext {
+    int dummy;
+};
+
+BidiContext *bidi_new_context(void)
+{
+    BidiContext *ctx = snew(BidiContext);
+    memset(ctx, 0, sizeof(BidiContext));
+    return ctx;
+}
+
+void bidi_free_context(BidiContext *ctx)
+{
+    sfree(ctx);
+}
+
 /*
  * The Main Bidi Function, and the only function that should
  * be used by the outside world.
@@ -1124,7 +1140,7 @@ int do_shape(bidi_char *line, bidi_char *to, int count)
  * the Bidirectional algorithm to.
  */
 
-int do_bidi(bidi_char *line, int count)
+void do_bidi(BidiContext *ctx, bidi_char *line, size_t count)
 {
     unsigned char* types;
     unsigned char* levels;
@@ -1145,7 +1161,7 @@ int do_bidi(bidi_char *line, int count)
         }
     }
     if (!yes)
-        return L;
+        return;
 
     /* Initialize types, levels */
     types = snewn(count, unsigned char);
@@ -1565,7 +1581,7 @@ int do_bidi(bidi_char *line, int count)
      */
     sfree(types);
     sfree(levels);
-    return R;
+    return;
 }
 
 
diff --git a/terminal/terminal.c b/terminal/terminal.c
index ddeb1e94..dcdbfc6a 100644
--- a/terminal/terminal.c
+++ b/terminal/terminal.c
@@ -2048,6 +2048,8 @@ Terminal *term_init(Conf *myconf, struct unicode_data *ucsdata, TermWin *win)
     term->win_scrollbar_update_pending = false;
     term->win_palette_pending = false;
 
+    term->bidi_ctx = bidi_new_context();
+
     palette_reset(term, false);
 
     return term;
@@ -2107,6 +2109,8 @@ void term_free(Terminal *term)
     sfree(term->window_title);
     sfree(term->icon_title);
 
+    bidi_free_context(term->bidi_ctx);
+
     sfree(term);
 }
 
@@ -5662,7 +5666,7 @@ static termchar *term_bidi_line(Terminal *term, struct termline *ldata,
             }
 
             if(!term->no_bidi)
-                do_bidi(term->wcFrom, nbc);
+                do_bidi(term->bidi_ctx, term->wcFrom, nbc);
 
             if(!term->no_arabicshaping) {
                 do_shape(term->wcFrom, term->wcTo, nbc);
diff --git a/terminal/terminal.h b/terminal/terminal.h
index c463f7a8..75d08de7 100644
--- a/terminal/terminal.h
+++ b/terminal/terminal.h
@@ -353,6 +353,8 @@ struct terminal_tag {
     char *window_title, *icon_title;
     bool minimised;
 
+    BidiContext *bidi_ctx;
+
     /* Multi-layered colour palette. The colours from Conf (plus the
      * default xterm-256 ones that don't have Conf ids at all) have
      * lowest priority, followed by platform overrides if any,