diff --git a/src/core/evaluator.js b/src/core/evaluator.js
index 418ef0d1b..09f9cad5e 100644
--- a/src/core/evaluator.js
+++ b/src/core/evaluator.js
@@ -1567,6 +1567,21 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
           hash.update(encoding.name);
         } else if (isRef(encoding)) {
           hash.update(encoding.num + '_' + encoding.gen);
+        } else if (isDict(encoding)) {
+          var keys = encoding.getKeys();
+          for (var i = 0, ii = keys.length; i < ii; i++) {
+            var entry = encoding.getRaw(keys[i]);
+            if (isName(entry)) {
+              hash.update(entry.name);
+            } else if (isRef(entry)) {
+              hash.update(entry.num + '_' + entry.gen);
+            } else if (isArray(entry)) { // 'Differences' entry.
+              // Ideally we should check the contents of the array, but to avoid
+              // parsing it here and then again in |extractDataStructures|,
+              // we only use the array length for now (fixes bug1157493.pdf).
+              hash.update(entry.length.toString());
+            }
+          }
         }
 
         var toUnicode = dict.get('ToUnicode') || baseDict.get('ToUnicode');
diff --git a/src/core/obj.js b/src/core/obj.js
index 833ca4215..29b4a8742 100644
--- a/src/core/obj.js
+++ b/src/core/obj.js
@@ -192,6 +192,10 @@ var Dict = (function DictClosure() {
       return all;
     },
 
+    getKeys: function Dict_getKeys() {
+      return Object.keys(this.map);
+    },
+
     set: function Dict_set(key, value) {
       this.map[key] = value;
     },
diff --git a/test/pdfs/.gitignore b/test/pdfs/.gitignore
index 354444578..e9d8d0e59 100644
--- a/test/pdfs/.gitignore
+++ b/test/pdfs/.gitignore
@@ -32,6 +32,7 @@
 !bug894572.pdf
 !bug911034.pdf
 !bug1108301.pdf
+!bug1157493.pdf
 !pdfjsbad1586.pdf
 !freeculture.pdf
 !pdfkit_compressed.pdf
diff --git a/test/pdfs/bug1157493.pdf b/test/pdfs/bug1157493.pdf
new file mode 100644
index 000000000..0dfef2218
Binary files /dev/null and b/test/pdfs/bug1157493.pdf differ
diff --git a/test/test_manifest.json b/test/test_manifest.json
index e136ebcfc..da0a9db36 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -1164,6 +1164,13 @@
        "link": false,
        "type": "eq"
     },
+    {  "id": "bug1157493",
+       "file": "pdfs/bug1157493.pdf",
+       "md5": "df96eddacf186c28a91e699800180c4f",
+       "rounds": 1,
+       "link": false,
+       "type": "eq"
+    },
     {  "id": "issue1466",
       "file": "pdfs/issue1466.pdf",
       "md5": "8a8877432e5bb10cfd50d60488d947bb",