diff --git unix/tclUnixChan.c unix/tclUnixChan.c
index 2f512266cd..67f22ff497 100644
--- unix/tclUnixChan.c
+++ unix/tclUnixChan.c
@@ -477,6 +477,20 @@ FileWideSeekProc(
  *----------------------------------------------------------------------
  */
 
+/*
+ * Bug ad5a57f2f271: Tcl_NotifyChannel is not a Tcl_FileProc,
+ * so do not pass it to directly to Tcl_CreateFileHandler.
+ * Instead, pass a wrapper which is a Tcl_FileProc.
+ */
+static void
+FileWatchNotifyChannelWrapper(
+    ClientData clientData,
+    int mask)
+{
+    Tcl_Channel channel = clientData;
+    Tcl_NotifyChannel(channel, mask);
+}
+
 static void
 FileWatchProc(
     ClientData instanceData,	/* The file state. */
@@ -487,15 +501,13 @@ FileWatchProc(
     FileState *fsPtr = instanceData;
 
     /*
-     * Make sure we only register for events that are valid on this file. Note
-     * that we are passing Tcl_NotifyChannel directly to Tcl_CreateFileHandler
-     * with the channel pointer as the client data.
+     * Make sure we only register for events that are valid on this file.
      */
 
     mask &= fsPtr->validMask;
     if (mask) {
 	Tcl_CreateFileHandler(fsPtr->fd, mask,
-		(Tcl_FileProc *) Tcl_NotifyChannel, fsPtr->channel);
+		FileWatchNotifyChannelWrapper, fsPtr->channel);
     } else {
 	Tcl_DeleteFileHandler(fsPtr->fd);
     }
diff --git unix/tclUnixPipe.c unix/tclUnixPipe.c
index 96ca095ea1..1dc0c8033b 100644
--- unix/tclUnixPipe.c
+++ unix/tclUnixPipe.c
@@ -1215,6 +1215,20 @@ PipeOutputProc(
  *----------------------------------------------------------------------
  */
 
+/*
+ * Bug ad5a57f2f271: Tcl_NotifyChannel is not a Tcl_FileProc,
+ * so do not pass it to directly to Tcl_CreateFileHandler.
+ * Instead, pass a wrapper which is a Tcl_FileProc.
+ */
+static void
+PipeWatchNotifyChannelWrapper(
+    ClientData clientData,
+    int mask)
+{
+    Tcl_Channel channel = clientData;
+    Tcl_NotifyChannel(channel, mask);
+}
+
 static void
 PipeWatchProc(
     ClientData instanceData,	/* The pipe state. */
@@ -1229,7 +1243,7 @@ PipeWatchProc(
 	newmask = mask & (TCL_READABLE | TCL_EXCEPTION);
 	if (newmask) {
 	    Tcl_CreateFileHandler(GetFd(psPtr->inFile), newmask,
-		    (Tcl_FileProc *) Tcl_NotifyChannel, psPtr->channel);
+		    PipeWatchNotifyChannelWrapper, psPtr->channel);
 	} else {
 	    Tcl_DeleteFileHandler(GetFd(psPtr->inFile));
 	}
@@ -1238,7 +1252,7 @@ PipeWatchProc(
 	newmask = mask & (TCL_WRITABLE | TCL_EXCEPTION);
 	if (newmask) {
 	    Tcl_CreateFileHandler(GetFd(psPtr->outFile), newmask,
-		    (Tcl_FileProc *) Tcl_NotifyChannel, psPtr->channel);
+		    PipeWatchNotifyChannelWrapper, psPtr->channel);
 	} else {
 	    Tcl_DeleteFileHandler(GetFd(psPtr->outFile));
 	}
