diff --git a/flang/lib/Lower/RTBuilder.h b/flang/lib/Lower/RTBuilder.h
--- a/flang/lib/Lower/RTBuilder.h
+++ b/flang/lib/Lower/RTBuilder.h
@@ -22,6 +22,7 @@
 #include "mlir/IR/MLIRContext.h"
 #include "mlir/IR/StandardTypes.h"
 #include "llvm/ADT/SmallVector.h"
+#include <complex>
 #include <functional>
 
 // List the runtime headers we want to be able to dissect
@@ -158,13 +159,13 @@
 }
 
 template <>
-constexpr TypeBuilderFunc getModel<float _Complex>() {
+constexpr TypeBuilderFunc getModel<std::complex<float>>() {
   return [](mlir::MLIRContext *context) -> mlir::Type {
     return fir::CplxType::get(context, sizeof(float));
   };
 }
 template <>
-constexpr TypeBuilderFunc getModel<double _Complex>() {
+constexpr TypeBuilderFunc getModel<std::complex<double>>() {
   return [](mlir::MLIRContext *context) -> mlir::Type {
     return fir::CplxType::get(context, sizeof(double));
   };