diff --git a/flang/runtime/io-api.cpp b/flang/runtime/io-api.cpp
--- a/flang/runtime/io-api.cpp
+++ b/flang/runtime/io-api.cpp
@@ -400,7 +400,7 @@
 }
 Cookie IONAME(BeginWaitAll)(
     ExternalUnit unitNumber, const char *sourceFile, int sourceLine) {
-  return IONAME(BeginWait)(unitNumber, 0 /*no ID=*/);
+  return IONAME(BeginWait)(unitNumber, 0 /*no ID=*/, sourceFile, sourceLine);
 }
 
 Cookie IONAME(BeginClose)(
diff --git a/flang/runtime/unit.h b/flang/runtime/unit.h
--- a/flang/runtime/unit.h
+++ b/flang/runtime/unit.h
@@ -39,6 +39,7 @@
   explicit ExternalFileUnit(int unitNumber) : unitNumber_{unitNumber} {
     isUTF8 = executionEnvironment.defaultUTF8;
     asyncIdAvailable_.set();
+    asyncIdAvailable_.reset(0);
   }
   ~ExternalFileUnit() {}
 
diff --git a/flang/runtime/unit.cpp b/flang/runtime/unit.cpp
--- a/flang/runtime/unit.cpp
+++ b/flang/runtime/unit.cpp
@@ -918,11 +918,13 @@
 }
 
 bool ExternalFileUnit::Wait(int id) {
-  if (id < 0 || asyncIdAvailable_.test(id)) {
+  if (static_cast<std::size_t>(id) >= asyncIdAvailable_.size() ||
+      asyncIdAvailable_.test(id)) {
     return false;
   } else {
-    if (id == 0) {
+    if (id == 0) { // means "all IDs"
       asyncIdAvailable_.set();
+      asyncIdAvailable_.reset(0);
     } else {
       asyncIdAvailable_.set(id);
     }