diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp
index 615e584f81..0436aa5428 100644
--- a/src/corelib/io/qprocess.cpp
+++ b/src/corelib/io/qprocess.cpp
@@ -903,6 +903,9 @@ void QProcessPrivate::cleanup()
 bool QProcessPrivate::tryReadFromChannel(Channel *channel)
 {
     Q_Q(QProcess);
+    if (channel->pipe[0] == INVALID_Q_PIPE)
+        return false;
+
     qint64 available = bytesAvailableInChannel(channel);
     if (available == 0) {
         if (channel->notifier)
diff --git a/src/corelib/io/qprocess_unix.cpp b/src/corelib/io/qprocess_unix.cpp
index 430393d6f2..3c1eeb5f91 100644
--- a/src/corelib/io/qprocess_unix.cpp
+++ b/src/corelib/io/qprocess_unix.cpp
@@ -965,6 +965,7 @@ bool QProcessPrivate::processStarted()
 
 qint64 QProcessPrivate::bytesAvailableInChannel(const Channel *channel) const
 {
+    Q_ASSERT(channel->pipe[0] != INVALID_Q_PIPE);
     int nbytes = 0;
     qint64 available = 0;
     if (::ioctl(channel->pipe[0], FIONREAD, (char *) &nbytes) >= 0)
@@ -977,6 +978,7 @@ qint64 QProcessPrivate::bytesAvailableInChannel(const Channel *channel) const
 
 qint64 QProcessPrivate::readFromChannel(const Channel *channel, char *data, qint64 maxlen)
 {
+    Q_ASSERT(channel->pipe[0] != INVALID_Q_PIPE);
     qint64 bytesRead = qt_safe_read(channel->pipe[0], data, maxlen);
 #if defined QPROCESS_DEBUG
     qDebug("QProcessPrivate::readFromChannel(%d, %p \"%s\", %lld) == %lld",
diff --git a/src/corelib/io/qprocess_win.cpp b/src/corelib/io/qprocess_win.cpp
index 2dd4c475d8..7b3f1f8f58 100644
--- a/src/corelib/io/qprocess_win.cpp
+++ b/src/corelib/io/qprocess_win.cpp
@@ -566,11 +566,8 @@ bool QProcessPrivate::processStarted()
 
 qint64 QProcessPrivate::bytesAvailableInChannel(const Channel *channel) const
 {
-    if (channel->pipe[0] == INVALID_Q_PIPE)
-        return 0;
-
-    if (!channel->reader)
-        return 0;
+    Q_ASSERT(channel->pipe[0] != INVALID_Q_PIPE);
+    Q_ASSERT(channel->reader);
 
     DWORD bytesAvail = channel->reader->bytesAvailable();
 #if defined QPROCESS_DEBUG
@@ -581,7 +578,9 @@ qint64 QProcessPrivate::bytesAvailableInChannel(const Channel *channel) const
 
 qint64 QProcessPrivate::readFromChannel(const Channel *channel, char *data, qint64 maxlen)
 {
-    return channel->reader ? channel->reader->read(data, maxlen) : 0;
+    Q_ASSERT(channel->pipe[0] != INVALID_Q_PIPE);
+    Q_ASSERT(channel->reader);
+    return channel->reader->read(data, maxlen);
 }
 
 static BOOL QT_WIN_CALLBACK qt_terminateApp(HWND hwnd, LPARAM procId)