diff --git a/src/core/evaluator.js b/src/core/evaluator.js
index b85101336..266800c41 100644
--- a/src/core/evaluator.js
+++ b/src/core/evaluator.js
@@ -263,8 +263,14 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
           groupOptions.isolated = (group.get('I') || false);
           groupOptions.knockout = (group.get('K') || false);
           if (group.has('CS')) {
-            colorSpace = ColorSpace.parse(group.get('CS'), this.xref, resources,
-                                          this.pdfFunctionFactory);
+            colorSpace = group.get('CS');
+            if (colorSpace) {
+              colorSpace = ColorSpace.parse(colorSpace, this.xref, resources,
+                                            this.pdfFunctionFactory);
+            } else {
+              warn('buildFormXObject - invalid/non-existent Group /CS entry: ' +
+                   group.getRaw('CS'));
+            }
           }
         }
 
diff --git a/test/pdfs/.gitignore b/test/pdfs/.gitignore
index ebcd5489c..9e753c24f 100644
--- a/test/pdfs/.gitignore
+++ b/test/pdfs/.gitignore
@@ -80,6 +80,7 @@
 !issue10542_reduced.pdf
 !issue10665_reduced.pdf
 !issue11016_reduced.pdf
+!issue11045.pdf
 !bad-PageLabels.pdf
 !decodeACSuccessive.pdf
 !filled-background.pdf
diff --git a/test/pdfs/issue11045.pdf b/test/pdfs/issue11045.pdf
new file mode 100644
index 000000000..e0ec598e2
Binary files /dev/null and b/test/pdfs/issue11045.pdf differ
diff --git a/test/test_manifest.json b/test/test_manifest.json
index 612975d54..09bc231c6 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -2888,6 +2888,13 @@
        "rounds": 1,
        "type": "eq"
     },
+    {  "id": "issue11045",
+       "file": "pdfs/issue11045.pdf",
+       "md5": "101d4cb649cc006e0f2b14923e8d97d6",
+       "rounds": 1,
+       "link": false,
+       "type": "eq"
+    },
     {  "id": "issue4890",
        "file": "pdfs/issue4890.pdf",
        "md5": "1666feb4cd26318c2bdbea6a175dce87",