diff --git a/src/calibre/ebooks/pdf/render/fonts.py b/src/calibre/ebooks/pdf/render/fonts.py
index a95c5f5271..a9a1fc795e 100644
--- a/src/calibre/ebooks/pdf/render/fonts.py
+++ b/src/calibre/ebooks/pdf/render/fonts.py
@@ -115,7 +115,7 @@ class Font(object):
         self.font_stream = FontStream(metrics.is_otf, compress=compress)
         self.font_descriptor = Dictionary({
             'Type': Name('FontDescriptor'),
-            'FontName': Name(metrics.postscript_name),
+            'FontName': Name('%s+%s'%(self.subset_tag, metrics.postscript_name)),
             'Flags': 0b100, # Symbolic font
             'FontBBox': Array(metrics.pdf_bbox),
             'ItalicAngle': metrics.post.italic_angle,