diff --git a/src/display/pattern_helper.js b/src/display/pattern_helper.js
index 4241695a23aa1..077ec990be87f 100644
--- a/src/display/pattern_helper.js
+++ b/src/display/pattern_helper.js
@@ -313,8 +313,8 @@ class MeshShadingPattern extends BaseShadingPattern {
     this._colors = IR[3];
     this._figures = IR[4];
     this._bounds = IR[5];
-    this._bbox = IR[7];
-    this._background = IR[8];
+    this._bbox = IR[6];
+    this._background = IR[7];
     this.matrix = null;
   }
 
diff --git a/test/pdfs/.gitignore b/test/pdfs/.gitignore
index b9b4efbd2fc69..7b9182629a57d 100644
--- a/test/pdfs/.gitignore
+++ b/test/pdfs/.gitignore
@@ -94,6 +94,7 @@
 !issue8424.pdf
 !issue8480.pdf
 !bug1650302_reduced.pdf
+!issue18816.pdf
 !issue8570.pdf
 !issue8697.pdf
 !issue8702.pdf
diff --git a/test/pdfs/issue18816.pdf b/test/pdfs/issue18816.pdf
new file mode 100644
index 0000000000000..79b1c75e5f264
Binary files /dev/null and b/test/pdfs/issue18816.pdf differ
diff --git a/test/test_manifest.json b/test/test_manifest.json
index 1a274fb5b7511..e50d5cadf5471 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -10078,6 +10078,13 @@
     "annotations": true,
     "type": "eq"
   },
+  {
+    "id": "issue18816",
+    "file": "pdfs/issue18816.pdf",
+    "md5": "45f863f5b227f700ffea1210e4f80403",
+    "rounds": 1,
+    "type": "eq"
+  },
   {
     "id": "issue17794",
     "file": "pdfs/issue17794.pdf",