diff --git a/src/core/fonts.js b/src/core/fonts.js
index 262f9e96c..5a48bbe50 100644
--- a/src/core/fonts.js
+++ b/src/core/fonts.js
@@ -1073,6 +1073,7 @@ class Font {
           map[+charCode] = SupplementalGlyphMapForCalibri[charCode];
         }
       }
+
       // Always update the glyph mapping with the `cidToGidMap` when it exists
       // (fixes issue12418_reduced.pdf).
       if (cidToGidMap) {
@@ -1082,6 +1083,20 @@ class Font {
             map[+charCode] = cidToGidMap[cid];
           }
         }
+        // When the /CIDToGIDMap is "incomplete", fallback to the included
+        // /ToUnicode-map regardless of its encoding (fixes issue11915.pdf).
+        if (
+          cidToGidMap.length !== this.toUnicode.length &&
+          properties.hasIncludedToUnicodeMap &&
+          this.toUnicode instanceof IdentityToUnicodeMap
+        ) {
+          this.toUnicode.forEach(function (charCode, unicodeCharCode) {
+            const cid = map[charCode];
+            if (cidToGidMap[cid] === undefined) {
+              map[+charCode] = unicodeCharCode;
+            }
+          });
+        }
       }
 
       if (!(this.toUnicode instanceof IdentityToUnicodeMap)) {
diff --git a/test/pdfs/.gitignore b/test/pdfs/.gitignore
index c8845e4ee..acdf66ae4 100644
--- a/test/pdfs/.gitignore
+++ b/test/pdfs/.gitignore
@@ -355,6 +355,7 @@
 !tensor-allflags-withfunction.pdf
 !issue10084_reduced.pdf
 !issue4246.pdf
+!issue11915.pdf
 !js-authors.pdf
 !issue4461.pdf
 !issue4573.pdf
diff --git a/test/pdfs/issue11915.pdf b/test/pdfs/issue11915.pdf
new file mode 100644
index 000000000..30396554f
Binary files /dev/null and b/test/pdfs/issue11915.pdf differ
diff --git a/test/test_manifest.json b/test/test_manifest.json
index cbb51a523..508fc5208 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -2365,6 +2365,12 @@
        "link": false,
        "type": "text"
     },
+    {  "id": "issue11915",
+       "file": "pdfs/issue11915.pdf",
+       "md5": "c4f890b4a5b6f21653421856335181d5",
+       "rounds": 1,
+       "type": "eq"
+    },
     {  "id": "issue10614",
        "file": "pdfs/issue10614.pdf",
        "md5": "c41da60ce9af100cb78e1c2a6ba18232",