diff --git a/mlir/include/mlir/Support/MlirOptMain.h b/mlir/include/mlir/Support/MlirOptMain.h
--- a/mlir/include/mlir/Support/MlirOptMain.h
+++ b/mlir/include/mlir/Support/MlirOptMain.h
@@ -10,6 +10,9 @@
 //
 //===----------------------------------------------------------------------===//
 
+#ifndef MLIR_SUPPORT_MLIROPTMAIN_H
+#define MLIR_SUPPORT_MLIROPTMAIN_H
+
 #include "mlir/Support/LogicalResult.h"
 #include "llvm/ADT/StringRef.h"
 
@@ -59,3 +62,5 @@
                           bool preloadDialectsInContext = true);
 
 } // end namespace mlir
+
+#endif // MLIR_SUPPORT_MLIROPTMAIN_H