diff --git a/src/core/fonts.js b/src/core/fonts.js
index c562ce12a..29f186fa3 100644
--- a/src/core/fonts.js
+++ b/src/core/fonts.js
@@ -3293,7 +3293,10 @@ class Font {
     return builder.toArray();
   }
 
-  get spaceWidth() {
+  /**
+   * @private
+   */
+  get _spaceWidth() {
     // trying to estimate space character width
     const possibleSpaceReplacements = ["space", "minus", "one", "i", "I"];
     let width;
@@ -3328,7 +3331,7 @@ class Font {
         break; // the non-zero width found
       }
     }
-    return shadow(this, "spaceWidth", width || this.defaultWidth);
+    return shadow(this, "_spaceWidth", width || this.defaultWidth);
   }
 
   /**
@@ -3376,6 +3379,13 @@ class Font {
         // .notdef glyphs should be invisible in non-embedded Type1 fonts, so
         // replace them with spaces.
         fontCharCode = 0x20;
+
+        if (glyphName === "") {
+          // Ensure that other relevant glyph properties are also updated
+          // (fixes issue18059.pdf).
+          width ||= this._spaceWidth;
+          unicode = String.fromCharCode(fontCharCode);
+        }
       }
       fontCharCode = mapSpecialUnicodeValues(fontCharCode);
     }
diff --git a/test/pdfs/.gitignore b/test/pdfs/.gitignore
index 13450e37c..7eedf8be6 100644
--- a/test/pdfs/.gitignore
+++ b/test/pdfs/.gitignore
@@ -56,6 +56,7 @@
 !issue17679_2.pdf
 !issue18030.pdf
 !issue18042.pdf
+!issue18059.pdf
 !issue14953.pdf
 !issue15367.pdf
 !issue15372.pdf
diff --git a/test/pdfs/issue18059.pdf b/test/pdfs/issue18059.pdf
new file mode 100644
index 000000000..82416e266
Binary files /dev/null and b/test/pdfs/issue18059.pdf differ
diff --git a/test/test_manifest.json b/test/test_manifest.json
index b7d1190f6..90ad056ec 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -2990,6 +2990,20 @@
     "rounds": 1,
     "type": "text"
   },
+  {
+    "id": "issue18059",
+    "file": "pdfs/issue18059.pdf",
+    "md5": "b70373894edfcd571a41caa1a0776b6f",
+    "rounds": 1,
+    "type": "eq"
+  },
+  {
+    "id": "issue18059-text",
+    "file": "pdfs/issue18059.pdf",
+    "md5": "b70373894edfcd571a41caa1a0776b6f",
+    "rounds": 1,
+    "type": "text"
+  },
   {
     "id": "issue11139",
     "file": "pdfs/issue11139.pdf",