diff --git a/core/fpdfapi/parser/cpdf_dictionary.cpp b/core/fpdfapi/parser/cpdf_dictionary.cpp
index 2f77a60..daeb765 100644
--- a/core/fpdfapi/parser/cpdf_dictionary.cpp
+++ b/core/fpdfapi/parser/cpdf_dictionary.cpp
@@ -211,6 +211,7 @@
 CPDF_Object* CPDF_Dictionary::SetFor(const ByteString& key,
                                      RetainPtr<CPDF_Object> pObj) {
   CHECK(!key.IsEmpty());
+  CHECK(key.AsStringView().IsASCII());
   CHECK(!IsLocked());
   if (!pObj) {
     m_Map.erase(key);
diff --git a/core/fpdfapi/parser/cpdf_syntax_parser.cpp b/core/fpdfapi/parser/cpdf_syntax_parser.cpp
index 47f4f1a..2560e98 100644
--- a/core/fpdfapi/parser/cpdf_syntax_parser.cpp
+++ b/core/fpdfapi/parser/cpdf_syntax_parser.cpp
@@ -592,7 +592,9 @@
       // `key` has to be "/X" at the minimum.
       if (key.GetLength() > 1) {
         ByteString key_no_slash(key.raw_str() + 1, key.GetLength() - 1);
-        pDict->SetFor(key_no_slash, std::move(pObj));
+        // `key_no_slash` must be ASCII, per PDF 32000 standard, section 7.2.1.
+        if (key_no_slash.AsStringView().IsASCII())
+          pDict->SetFor(key_no_slash, std::move(pObj));
       }
     }
 
diff --git a/testing/resources/bad_dict_keys.in b/testing/resources/bad_dict_keys.in
index 3f53c28..9eb648b 100644
--- a/testing/resources/bad_dict_keys.in
+++ b/testing/resources/bad_dict_keys.in
@@ -10,6 +10,7 @@
   /Count 1
   /Kids [3 0 R]
   / [3 0 R]
+  /#80 [3 0 R]
 >>
 endobj
 {{object 3 0}} <<
diff --git a/testing/resources/bad_dict_keys.pdf b/testing/resources/bad_dict_keys.pdf
index b55c434..9ab931c 100644
--- a/testing/resources/bad_dict_keys.pdf
+++ b/testing/resources/bad_dict_keys.pdf
@@ -11,6 +11,7 @@
   /Count 1
   /Kids [3 0 R]
   / [3 0 R]
+  /#80 [3 0 R]
 >>
 endobj
 3 0 obj <<
@@ -23,11 +24,11 @@
 0000000000 65535 f 
 0000000015 00000 n 
 0000000068 00000 n 
-0000000169 00000 n 
+0000000184 00000 n 
 trailer <<
   /Root 1 0 R
   /Size 4
 >>
 startxref
-220
+235
 %%EOF