Index: flang/lib/Semantics/check-omp-structure.cpp
===================================================================
--- flang/lib/Semantics/check-omp-structure.cpp
+++ flang/lib/Semantics/check-omp-structure.cpp
@@ -127,7 +127,7 @@
     // 2.7.2 end-sections -> END SECTIONS [nowait-clause]
   case llvm::omp::Directive::OMPD_sections:
     SetContextDirectiveEnum(llvm::omp::Directive::OMPD_end_sections);
-    SetContextAllowed(OmpClauseSet{llvm::omp::Clause::OMPC_nowait});
+    SetContextAllowedOnce(OmpClauseSet{llvm::omp::Clause::OMPC_nowait});
     break;
   default:
     // no clauses are allowed
Index: flang/test/Semantics/omp-clause-validity01.f90
===================================================================
--- flang/test/Semantics/omp-clause-validity01.f90
+++ flang/test/Semantics/omp-clause-validity01.f90
@@ -261,6 +261,17 @@
   d = 2
   !ERROR: NUM_THREADS clause is not allowed on the END SECTIONS directive
   !$omp end sections num_threads(4)
+
+  !$omp parallel
+  !$omp sections
+    b = 1
+  !$omp section
+    c = 1
+    d = 2
+  !ERROR: At most one NOWAIT clause can appear on the END SECTIONS directive
+  !$omp end sections nowait nowait
+  !$omp end parallel
+
   !$omp end parallel
 
 ! 2.11.2 parallel-sections-clause -> parallel-clause |