diff --git a/flang/lib/Semantics/check-acc-structure.h b/flang/lib/Semantics/check-acc-structure.h
--- a/flang/lib/Semantics/check-acc-structure.h
+++ b/flang/lib/Semantics/check-acc-structure.h
@@ -115,6 +115,8 @@
       const llvm::acc::Directive directive,
       const parser::CharBlock &directiveSource) const;
 
+  bool CheckAllowedModifier(llvm::acc::Clause clause);
+
   llvm::StringRef getClauseName(llvm::acc::Clause clause) override;
   llvm::StringRef getDirectiveName(llvm::acc::Directive directive) override;
 };
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
@@ -121,6 +121,19 @@
   llvm::acc::Directive currentDirective_;
 };
 
+bool AccStructureChecker::CheckAllowedModifier(llvm::acc::Clause clause) {
+  if (GetContext().directive == llvm::acc::ACCD_enter_data ||
+      GetContext().directive == llvm::acc::ACCD_exit_data) {
+    context_.Say(GetContext().clauseSource,
+        "Modifier is not allowed for the %s clause "
+        "on the %s directive"_err_en_US,
+        parser::ToUpperCaseLetters(getClauseName(clause).str()),
+        ContextDirectiveAsFortran());
+    return true;
+  }
+  return false;
+}
+
 void AccStructureChecker::Enter(const parser::AccClause &x) {
   SetContextClause(x);
 }
@@ -375,6 +388,8 @@
   const auto &modifierClause{c.v};
   if (const auto &modifier{
           std::get<std::optional<parser::AccDataModifier>>(modifierClause.t)}) {
+    if (CheckAllowedModifier(llvm::acc::Clause::ACCC_copyin))
+      return;
     if (modifier->v != parser::AccDataModifier::Modifier::ReadOnly) {
       context_.Say(GetContext().clauseSource,
           "Only the READONLY modifier is allowed for the %s clause "
@@ -392,6 +407,8 @@
   const auto &modifierClause{c.v};
   if (const auto &modifier{
           std::get<std::optional<parser::AccDataModifier>>(modifierClause.t)}) {
+    if (CheckAllowedModifier(llvm::acc::Clause::ACCC_copyout))
+      return;
     if (modifier->v != parser::AccDataModifier::Modifier::Zero) {
       context_.Say(GetContext().clauseSource,
           "Only the ZERO modifier is allowed for the %s clause "
diff --git a/flang/test/Semantics/acc-clause-validity.f90 b/flang/test/Semantics/acc-clause-validity.f90
--- a/flang/test/Semantics/acc-clause-validity.f90
+++ b/flang/test/Semantics/acc-clause-validity.f90
@@ -45,9 +45,12 @@
   !ERROR: At least one of ATTACH, COPYIN, CREATE clause must appear on the ENTER DATA directive
   !$acc enter data
 
-  !ERROR: Only the READONLY modifier is allowed for the COPYIN clause on the ENTER DATA directive
+  !ERROR: Modifier is not allowed for the COPYIN clause on the ENTER DATA directive
   !$acc enter data copyin(zero: i)
 
+  !ERROR: Modifier is not allowed for the COPYOUT clause on the EXIT DATA directive
+  !$acc exit data copyout(zero: i)
+
   !ERROR: Only the ZERO modifier is allowed for the CREATE clause on the ENTER DATA directive
   !$acc enter data create(readonly: i)