diff --git a/openmp/runtime/src/kmp_tasking.cpp b/openmp/runtime/src/kmp_tasking.cpp
--- a/openmp/runtime/src/kmp_tasking.cpp
+++ b/openmp/runtime/src/kmp_tasking.cpp
@@ -884,7 +884,8 @@
 
     // Only need to keep track of count if team parallel and tasking not
     // serialized
-    if (!(taskdata->td_flags.team_serial || taskdata->td_flags.tasking_ser)) {
+    if (!(taskdata->td_flags.team_serial || taskdata->td_flags.tasking_ser) ||
+        taskdata->td_flags.detachable == TASK_DETACHABLE) {
       // Predecrement simulated by "- 1" calculation
       children =
           KMP_ATOMIC_DEC(&taskdata->td_parent->td_incomplete_child_tasks) - 1;
diff --git a/openmp/runtime/test/tasking/omp_detach_taskwait.c b/openmp/runtime/test/tasking/omp_detach_taskwait.c
new file mode 100644
--- /dev/null
+++ b/openmp/runtime/test/tasking/omp_detach_taskwait.c
@@ -0,0 +1,23 @@
+// RUN: %libomp-compile -fopenmp-version=50 && env OMP_NUM_THREADS='3' %libomp-run
+// RUN: %libomp-compile -fopenmp-version=50 && env OMP_NUM_THREADS='1' %libomp-run
+
+// Checked gcc 9.2 does not support detach clause on task construct,
+// clang supports detach clause since version 11
+// UNSUPPORTED: gcc, clang-10, clang-9, clang-8, clang-7
+
+#include <omp.h>
+
+int main()
+{
+  #pragma omp parallel
+  #pragma omp master
+  {
+    omp_event_handle_t event;
+    #pragma omp task detach(event)
+    {
+      omp_fulfill_event(event);
+    }
+    #pragma omp taskwait
+  }
+  return 0;
+}