diff --git a/flang/lib/Evaluate/tools.cpp b/flang/lib/Evaluate/tools.cpp
index 2d0e1996632fc..16b0260719097 100644
--- a/flang/lib/Evaluate/tools.cpp
+++ b/flang/lib/Evaluate/tools.cpp
@@ -212,6 +212,11 @@ ConvertRealOperandsResult ConvertRealOperands(
             return {AsSameKindExprs<TypeCategory::Real>(
                 ConvertTo(ry, std::move(bx)), std::move(ry))};
           },
+          [&](BOZLiteralConstant &&,
+              BOZLiteralConstant &&) -> ConvertRealOperandsResult {
+            messages.Say("operands cannot both be BOZ"_err_en_US);
+            return std::nullopt;
+          },
           [&](auto &&, auto &&) -> ConvertRealOperandsResult { // C718
             messages.Say(
                 "operands must be INTEGER, UNSIGNED, REAL, or BOZ"_err_en_US);
diff --git a/flang/test/Semantics/complex01.f90 b/flang/test/Semantics/complex01.f90
index c9d408ee0e111..d268eafa68589 100644
--- a/flang/test/Semantics/complex01.f90
+++ b/flang/test/Semantics/complex01.f90
@@ -1,5 +1,5 @@
 ! RUN: %python %S/test_errors.py %s %flang_fc1
-! C718 Each named constant in a complex literal constant shall be of type 
+! C718 Each named constant in a complex literal constant shall be of type
 ! integer or real.
 subroutine s()
   integer :: ivar = 35
@@ -30,4 +30,6 @@ subroutine s()
   complex :: cvar11 = (cconst, 1.0)
   !ERROR: operands must be INTEGER, UNSIGNED, REAL, or BOZ
   complex :: cvar12 = (lconst, 1.0)
+  !ERROR: operands cannot both be BOZ
+  complex :: cvar13 = (z'3f700000', z'00000000')
 end subroutine s