diff --git a/pdf.js b/pdf.js
index 8cddc97b..7530865c 100644
--- a/pdf.js
+++ b/pdf.js
@@ -5190,7 +5190,7 @@ var PartialEvaluator = (function partialEvaluator() {
         if (isRef(df))
           df = xref.fetch(df);
 
-        dict = xref.fetch(isRef(df) ? df : df[0]);
+        dict = xref.fetchIfRef(isRef(df) ? df : df[0]);
 
         type = dict.get('Subtype');
         assertWellFormed(isName(type), 'invalid font Subtype');
diff --git a/test/pdfs/Test-plusminus.pdf b/test/pdfs/Test-plusminus.pdf
new file mode 100644
index 00000000..50ae29a2
Binary files /dev/null and b/test/pdfs/Test-plusminus.pdf differ
diff --git a/test/test_manifest.json b/test/test_manifest.json
index 15771438..43b799ba 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -43,6 +43,11 @@
        "rounds": 1,
        "type": "eq"
     },
+    {  "id": "plusminus",
+       "file": "pdfs/Test-plusminus.pdf",
+       "rounds": 1,
+       "type": "eq"
+    },
     {  "id": "openoffice-pdf",
        "file": "pdfs/DiwanProfile.pdf",
        "link": true,