diff --git a/flang/lib/Semantics/check-acc-structure.cpp b/flang/lib/Semantics/check-acc-structure.cpp
--- a/flang/lib/Semantics/check-acc-structure.cpp
+++ b/flang/lib/Semantics/check-acc-structure.cpp
@@ -438,6 +438,15 @@
                   .str()),
           ContextDirectiveAsFortran());
     }
+    if (GetContext().directive == llvm::acc::Directive::ACCD_declare) {
+      context_.Say(GetContext().clauseSource,
+          "The ZERO modifier is not allowed for the %s clause "
+          "on the %s directive"_err_en_US,
+          parser::ToUpperCaseLetters(
+              llvm::acc::getOpenACCClauseName(llvm::acc::Clause::ACCC_copyout)
+                  .str()),
+          ContextDirectiveAsFortran());
+    }
   }
 }
 
diff --git a/flang/test/Semantics/OpenACC/acc-declare-validity.f90 b/flang/test/Semantics/OpenACC/acc-declare-validity.f90
--- a/flang/test/Semantics/OpenACC/acc-declare-validity.f90
+++ b/flang/test/Semantics/OpenACC/acc-declare-validity.f90
@@ -57,4 +57,10 @@
     !$acc declare present(cc)
   end subroutine sub2
 
+  subroutine sub3()
+    real :: aa(100)
+    !ERROR: The ZERO modifier is not allowed for the COPYOUT clause on the DECLARE directive
+    !$acc declare copyout(zero: aa)
+  end subroutine
+
 end module openacc_declare_validity