diff --git a/src/hb-ot-shape-normalize.cc b/src/hb-ot-shape-normalize.cc
index 2a6a43900..0d2f8f57c 100644
--- a/src/hb-ot-shape-normalize.cc
+++ b/src/hb-ot-shape-normalize.cc
@@ -209,7 +209,14 @@ decompose_current_character (const hb_ot_shape_normalize_context_t *c, bool shor
   else if (decompose_compatibility (c, buffer->cur().codepoint))
     skip_char (buffer);
   else
+  {
+    /* Not found, not decomposible;  If codepoint is invalid Unicode and
+     * font supports U+FFFD REPLACEMENT CHARACTER, use that instead. */
+    hb_codepoint_t FFFD_glyph;
+    if (buffer->cur().codepoint > 0x10FFFF && c->font->get_glyph (0xFFFD, 0, &FFFD_glyph))
+      glyph = FFFD_glyph;
     next_char (buffer, glyph); /* glyph is initialized in earlier branches. */
+  }
 }
 
 static inline void