diff --git a/src/core/cmap.js b/src/core/cmap.js
index 3dd5f95fb..b43906537 100644
--- a/src/core/cmap.js
+++ b/src/core/cmap.js
@@ -996,7 +996,7 @@ var CMapFactory = (function CMapFactoryClosure() {
   }
 
   return {
-    create(params) {
+    async create(params) {
       var encoding = params.encoding;
       var fetchBuiltInCMap = params.fetchBuiltInCMap;
       var useCMap = params.useCMap;
@@ -1015,7 +1015,7 @@ var CMapFactory = (function CMapFactoryClosure() {
           return parsedCMap;
         });
       }
-      return Promise.reject(new Error("Encoding required."));
+      throw new Error("Encoding required.");
     },
   };
 })();
diff --git a/src/core/evaluator.js b/src/core/evaluator.js
index 2f8a88126..344540143 100644
--- a/src/core/evaluator.js
+++ b/src/core/evaluator.js
@@ -2612,31 +2612,48 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
           encoding: cmapObj,
           fetchBuiltInCMap: this.fetchBuiltInCMap,
           useCMap: null,
-        }).then(function(cmap) {
-          if (cmap instanceof IdentityCMap) {
-            return new IdentityToUnicodeMap(0, 0xffff);
-          }
-          var map = new Array(cmap.length);
-          // Convert UTF-16BE
-          // NOTE: cmap can be a sparse array, so use forEach instead of for(;;)
-          // to iterate over all keys.
-          cmap.forEach(function(charCode, token) {
-            var str = [];
-            for (var k = 0; k < token.length; k += 2) {
-              var w1 = (token.charCodeAt(k) << 8) | token.charCodeAt(k + 1);
-              if ((w1 & 0xf800) !== 0xd800) {
-                // w1 < 0xD800 || w1 > 0xDFFF
-                str.push(w1);
-                continue;
-              }
-              k += 2;
-              var w2 = (token.charCodeAt(k) << 8) | token.charCodeAt(k + 1);
-              str.push(((w1 & 0x3ff) << 10) + (w2 & 0x3ff) + 0x10000);
+        }).then(
+          function(cmap) {
+            if (cmap instanceof IdentityCMap) {
+              return new IdentityToUnicodeMap(0, 0xffff);
             }
-            map[charCode] = String.fromCodePoint.apply(String, str);
-          });
-          return new ToUnicodeMap(map);
-        });
+            var map = new Array(cmap.length);
+            // Convert UTF-16BE
+            // NOTE: cmap can be a sparse array, so use forEach instead of
+            // `for(;;)` to iterate over all keys.
+            cmap.forEach(function(charCode, token) {
+              var str = [];
+              for (var k = 0; k < token.length; k += 2) {
+                var w1 = (token.charCodeAt(k) << 8) | token.charCodeAt(k + 1);
+                if ((w1 & 0xf800) !== 0xd800) {
+                  // w1 < 0xD800 || w1 > 0xDFFF
+                  str.push(w1);
+                  continue;
+                }
+                k += 2;
+                var w2 = (token.charCodeAt(k) << 8) | token.charCodeAt(k + 1);
+                str.push(((w1 & 0x3ff) << 10) + (w2 & 0x3ff) + 0x10000);
+              }
+              map[charCode] = String.fromCodePoint.apply(String, str);
+            });
+            return new ToUnicodeMap(map);
+          },
+          reason => {
+            if (reason instanceof AbortException) {
+              return null;
+            }
+            if (this.options.ignoreErrors) {
+              // Error in the ToUnicode data -- sending unsupported feature
+              // notification and allow font parsing to continue.
+              this.handler.send("UnsupportedFeature", {
+                featureId: UNSUPPORTED_FEATURES.font,
+              });
+              warn(`readToUnicode - ignoring ToUnicode data: "${reason}".`);
+              return null;
+            }
+            throw reason;
+          }
+        );
       }
       return Promise.resolve(null);
     },
diff --git a/test/pdfs/.gitignore b/test/pdfs/.gitignore
index d55596365..c2392001c 100644
--- a/test/pdfs/.gitignore
+++ b/test/pdfs/.gitignore
@@ -352,6 +352,7 @@
 !issue7878.pdf
 !font_ascent_descent.pdf
 !issue11442_reduced.pdf
+!issue11549_reduced.pdf
 !issue8097_reduced.pdf
 !transparent.pdf
 !xobject-image.pdf
diff --git a/test/pdfs/issue11549_reduced.pdf b/test/pdfs/issue11549_reduced.pdf
new file mode 100644
index 000000000..e9e8ee66f
Binary files /dev/null and b/test/pdfs/issue11549_reduced.pdf differ
diff --git a/test/test_manifest.json b/test/test_manifest.json
index 014981764..b737f2a1d 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -60,6 +60,13 @@
        "link": false,
        "type": "eq"
     },
+    {  "id": "issue11549",
+       "file": "pdfs/issue11549_reduced.pdf",
+       "md5": "a1ea636f413e02e10dbdf379ab4a99ae",
+       "rounds": 1,
+       "link": false,
+       "type": "eq"
+    },
     {  "id": "issue1293",
        "file": "pdfs/issue1293r.pdf",
        "md5": "4a098f5051f34fab036f5bbe88f8deef",