diff --git a/flang/lib/Lower/OpenMP.cpp b/flang/lib/Lower/OpenMP.cpp
--- a/flang/lib/Lower/OpenMP.cpp
+++ b/flang/lib/Lower/OpenMP.cpp
@@ -2307,6 +2307,7 @@
                     // Match the pattern here.
                     mlir::Operation *reductionOp =
                         findReductionChain(loadVal, &reductionVal);
+                    if (reductionOp == nullptr) continue;
                     assert(mlir::isa<mlir::arith::SelectOp>(reductionOp) &&
                            "Selection Op not found in reduction intrinsic");
                     mlir::Operation *compareOp =
diff --git a/flang/test/Lower/OpenMP/wsloop-reduction-max.f90 b/flang/test/Lower/OpenMP/wsloop-reduction-max.f90
--- a/flang/test/Lower/OpenMP/wsloop-reduction-max.f90
+++ b/flang/test/Lower/OpenMP/wsloop-reduction-max.f90
@@ -63,4 +63,13 @@
   !$omp end do
   !$omp end parallel
   print *, x
+
+  !$omp parallel
+  !$omp do reduction(max:x)
+  do i=1, 100
+    if (y(i) .gt. x) x = y(i)
+  end do
+  !$omp end do
+  !$omp end parallel
+  print *, x
 end subroutine