diff --git a/go/ast/astutil/imports.go b/go/ast/astutil/imports.go
index 36c536b5..4a77c782 100644
--- a/go/ast/astutil/imports.go
+++ b/go/ast/astutil/imports.go
@@ -262,7 +262,7 @@ func DeleteNamedImport(fset *token.FileSet, f *ast.File, name, path string) (del
 					// There was a blank line immediately preceding the deleted import,
 					// so there's no need to close the hole.
 					// Do nothing.
-				} else {
+				} else if line != fset.File(gen.Rparen).LineCount() {
 					// There was no blank line. Close the hole.
 					fset.File(gen.Rparen).MergeLine(line)
 				}
diff --git a/go/ast/astutil/imports_test.go b/go/ast/astutil/imports_test.go
index cb12a290..21682674 100644
--- a/go/ast/astutil/imports_test.go
+++ b/go/ast/astutil/imports_test.go
@@ -1297,6 +1297,21 @@ import (
 	/* comment 2 */
 	"io"
 )
+`,
+	},
+
+	// Issue 20229: MergeLine panic on weird input
+	{
+		name: "import.37",
+		pkg:  "io",
+		in: `package main
+import("_"
+"io")`,
+		out: `package main
+
+import (
+	"_"
+)
 `,
 	},
 }