diff --git a/src/core/cff_parser.js b/src/core/cff_parser.js
index 2e2b811e4..a6c7bae35 100644
--- a/src/core/cff_parser.js
+++ b/src/core/cff_parser.js
@@ -1556,7 +1556,9 @@ class CFFCompiler {
   }
 
   compileHeader(header) {
-    return [header.major, header.minor, header.hdrSize, header.offSize];
+    // `header.hdrSize` can be any value but we only write 4 values
+    // so header size is 4 (prevents OTS from rejecting the font).
+    return [header.major, header.minor, 4, header.offSize];
   }
 
   compileNameIndex(names) {
diff --git a/test/pdfs/.gitignore b/test/pdfs/.gitignore
index 36e62e5e3..12f5eb3ff 100644
--- a/test/pdfs/.gitignore
+++ b/test/pdfs/.gitignore
@@ -337,6 +337,7 @@
 !issue4573.pdf
 !issue4722.pdf
 !issue4800.pdf
+!issue13147.pdf
 !issue11477_reduced.pdf
 !text_clip_cff_cid.pdf
 !issue4801.pdf
diff --git a/test/pdfs/issue13147.pdf b/test/pdfs/issue13147.pdf
new file mode 100644
index 000000000..cbc9cef93
Binary files /dev/null and b/test/pdfs/issue13147.pdf differ
diff --git a/test/test_manifest.json b/test/test_manifest.json
index 42c000b8f..fd9a72678 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -653,6 +653,12 @@
        "link": false,
        "type": "text"
     },
+    {  "id": "issue13147",
+       "file": "pdfs/issue13147.pdf",
+       "md5": "83db23f29b5e1a80d31d5069299e29cc",
+       "rounds": 1,
+       "type": "eq"
+    },
     {  "id": "fit11-talk",
        "file": "pdfs/fit11-talk.pdf",
        "md5": "eb7b224107205db4fea9f7df0185f77d",