diff --git a/flang/lib/Lower/Bridge.cpp b/flang/lib/Lower/Bridge.cpp
--- a/flang/lib/Lower/Bridge.cpp
+++ b/flang/lib/Lower/Bridge.cpp
@@ -2859,20 +2859,21 @@
 
               // Assignment to/from polymorphic entities are done with the
               // runtime.
-              if (lhsType->IsPolymorphic() ||
-                  lhsType->IsUnlimitedPolymorphic() ||
-                  rhsType->IsPolymorphic() ||
-                  rhsType->IsUnlimitedPolymorphic()) {
-                mlir::Value lhs;
-                if (Fortran::lower::isWholeAllocatable(assign.lhs))
-                  lhs = genExprMutableBox(loc, assign.lhs).getAddr();
-                else
-                  lhs = fir::getBase(genExprBox(loc, assign.lhs, stmtCtx));
-                mlir::Value rhs =
-                    fir::getBase(genExprBox(loc, assign.rhs, stmtCtx));
-                fir::runtime::genAssign(*builder, loc, lhs, rhs);
-                return;
-              }
+              if (rhsType) // Eliminate BOZ on rhs
+                if (lhsType->IsPolymorphic() ||
+                    lhsType->IsUnlimitedPolymorphic() ||
+                    rhsType->IsPolymorphic() ||
+                    rhsType->IsUnlimitedPolymorphic()) {
+                  mlir::Value lhs;
+                  if (Fortran::lower::isWholeAllocatable(assign.lhs))
+                    lhs = genExprMutableBox(loc, assign.lhs).getAddr();
+                  else
+                    lhs = fir::getBase(genExprBox(loc, assign.lhs, stmtCtx));
+                  mlir::Value rhs =
+                      fir::getBase(genExprBox(loc, assign.rhs, stmtCtx));
+                  fir::runtime::genAssign(*builder, loc, lhs, rhs);
+                  return;
+                }
 
               // Note: No ad-hoc handling for pointers is required here. The
               // target will be assigned as per 2018 10.2.1.3 p2. genExprAddr