diff --git a/src/main/scala/dxWDL/CompilerNative.scala b/src/main/scala/dxWDL/CompilerNative.scala
index da779d87..d839d532 100644
--- a/src/main/scala/dxWDL/CompilerNative.scala
+++ b/src/main/scala/dxWDL/CompilerNative.scala
@@ -122,9 +122,15 @@ object CompilerNative {
             |
             |    # setup any file streams. Keep track of background
             |    # processes in the 'background_pids' array.
+            |    # We 'source' the sub-script here, because we
+            |    # need to wait for the pids. This can only be done
+            |    # for child processes (not grand-children).
             |    if [[ -e $${HOME}/execution/meta/setup_streams ]]; then
-            |       cat $${HOME}/execution/meta/setup_streams
-            |       $${HOME}/execution/meta/setup_streams
+            |       source $${HOME}/execution/meta/setup_streams > $${HOME}/execution/meta/background_pids.txt
+            |
+            |       # reads the file line by line, and converts into a bash array
+            |       mapfile -t background_pids < $${HOME}/execution/meta/background_pids.txt
+            |       echo "Background processes ids: $${background_pids[@]}"
             |    fi
             |
             |    # Run the shell script generated by the prolog.
@@ -147,14 +153,21 @@ object CompilerNative {
             |    #  1) 'dx cat' returns zero status when a user reads only the beginning
             |    #  of a file
             |    for pid in $${background_pids[@]}; do
-            |        p_status=`ps --pid $$pid --no-headers | wc -l`
+            |        p_status=0
+            |        p_status=`ps --pid $$pid --no-headers | wc -l`  || p_status=0
+            |
             |        if [[ $$p_status == 0 ]]; then
             |            # the process is already dead, check correct exit status
-            |            wait $$pid
+            |            echo "wait $$pid"
+            |            rc=0
+            |            wait $$pid || rc=$$?
+            |            if [[ $$rc != 0 ]]; then
+            |                echo "Background download process $$pid failed"
+            |                exit $$rc
+            |            fi
             |        else
-            |            echo "Warning: background download process $$pid has not exited."
+            |            echo "Warning: background download process $$pid is still running."
             |            echo "Perhaps the worker process did not read it."
-            |            ps --pid $$pid -F
             |        fi
             |    done
             |
diff --git a/src/main/scala/dxWDL/RunnerTask.scala b/src/main/scala/dxWDL/RunnerTask.scala
index 0b62ebad..c11f35fd 100644
--- a/src/main/scala/dxWDL/RunnerTask.scala
+++ b/src/main/scala/dxWDL/RunnerTask.scala
@@ -238,15 +238,16 @@ case class RunnerTask(task:WdlTask,
     // file on the instance.
     private def handleStreamingFiles(inputs: Map[String, BValue])
             : (Option[String], Map[String, BValue]) = {
-        // A file that needs to be stream-downloaded.
-        // Make a named pipe, and stream the file from the platform to the pipe.
-        // Keep track of the download process. We need to ensure pipes have
-        // different names, even if the file-names are the same.
+        // A file that needs to be stream-downloaded. Make a named
+        // pipe, and stream the file from the platform to the pipe.
+        // Ensure pipes have different names, even if the
+        // file-names are the same. Write the process ids of the download jobs,
+        // to stdout. The calling script will keep track of them, and check
+        // for abnormal termination.
         //
-        // Note: all other files have already been downloaded.
+        // Note: at this point, all other files have already been downloaded.
         var fifoCount = 0
         def mkfifo(wvl: WdlVarLinks, path: String) : (WdlValue, String) = {
-            System.err.println(s"Creating named fifo for file ${path}, it will be streamed")
             val filename = Paths.get(path).toFile.getName
             val fifo:Path = Paths.get(Utils.DX_HOME, s"fifo_${fifoCount}_${filename}")
             fifoCount += 1
@@ -254,7 +255,7 @@ case class RunnerTask(task:WdlTask,
             val bashSnippet:String =
                 s"""|mkfifo ${fifo.toString}
                     |dx cat ${dxFileId} > ${fifo.toString} &
-                    |background_pids+=($$!)
+                    |echo $$!
                     |""".stripMargin
             (WdlSingleFile(fifo.toString), bashSnippet)
         }