diff --git a/0001-virt-df-parallel-Compile-debugging-messages-in-alway.patch b/0001-virt-df-parallel-Compile-debugging-messages-in-alway.patch
new file mode 100644
index 0000000..122c57e
--- /dev/null
+++ b/0001-virt-df-parallel-Compile-debugging-messages-in-alway.patch
@@ -0,0 +1,107 @@
+From d512fb4a1a98be294d11d5de88eabcfc2be8e964 Mon Sep 17 00:00:00 2001
+From: "Richard W.M. Jones" <rjones@redhat.com>
+Date: Tue, 3 Sep 2013 12:44:25 +0100
+Subject: [PATCH] virt-df: parallel: Compile debugging messages in always.
+
+Enable debugging messages whenever LIBGUESTFS_DEBUG=1 / -v option, so
+that we can track down possible race condition seen in Koji.
+---
+ df/parallel.c | 26 ++++++++++++++++++--------
+ 1 file changed, 18 insertions(+), 8 deletions(-)
+
+diff --git a/df/parallel.c b/df/parallel.c
+index a06e370..1a47b34 100644
+--- a/df/parallel.c
++++ b/df/parallel.c
+@@ -42,8 +42,6 @@
+ 
+ #if defined(HAVE_LIBVIRT)
+ 
+-#define DEBUG_PARALLEL 0
+-
+ /* Maximum number of threads we would ever run.  Note this should not
+  * be > 20, unless libvirt is modified to increase the maximum number
+  * of clients.
+@@ -70,6 +68,7 @@ static void thread_failure (const char *fn, int err);
+ static void *worker_thread (void *arg);
+ 
+ struct thread_data {
++  size_t thread_num;            /* Thread number. */
+   int trace, verbose;           /* Flags from the options_handle. */
+   work_fn work;
+   int r;                        /* Used to store the error status. */
+@@ -96,6 +95,7 @@ start_threads (size_t option_P, guestfs_h *options_handle, work_fn work)
+   pthread_t threads[nr_threads];
+ 
+   for (i = 0; i < nr_threads; ++i) {
++    thread_data[i].thread_num = i;
+     if (options_handle) {
+       thread_data[i].trace = guestfs_get_trace (options_handle);
+       thread_data[i].verbose = guestfs_get_verbose (options_handle);
+@@ -137,6 +137,9 @@ worker_thread (void *thread_data_vp)
+ 
+   thread_data->r = 0;
+ 
++  if (thread_data->verbose)
++    printf ("thread %zu starting\n", thread_data->thread_num);
++
+   while (1) {
+     size_t i;               /* The current domain we're working on. */
+     FILE *fp;
+@@ -146,6 +149,9 @@ worker_thread (void *thread_data_vp)
+     int err;
+ 
+     /* Take the next domain from the list. */
++    if (thread_data->verbose)
++      printf ("thread %zu waiting to get work\n", thread_data->thread_num);
++
+     err = pthread_mutex_lock (&take_mutex);
+     if (err != 0) {
+       thread_failure ("pthread_mutex_lock", err);
+@@ -163,8 +169,8 @@ worker_thread (void *thread_data_vp)
+     if (i >= nr_domains)        /* Work finished. */
+       break;
+ 
+-    if (DEBUG_PARALLEL)
+-      printf ("thread taking domain %zu\n", i);
++    if (thread_data->verbose)
++      printf ("thread %zu taking domain %zu\n", thread_data->thread_num, i);
+ 
+     fp = open_memstream (&output, &output_len);
+     if (fp == NULL) {
+@@ -195,6 +201,10 @@ worker_thread (void *thread_data_vp)
+     /* Retire this domain.  We have to retire domains in order, which
+      * may mean waiting for another thread to finish here.
+      */
++    if (thread_data->verbose)
++      printf ("thread %zu waiting to retire domain %zu\n",
++              thread_data->thread_num, i);
++
+     err = pthread_mutex_lock (&retire_mutex);
+     if (err != 0) {
+       thread_failure ("pthread_mutex_lock", err);
+@@ -210,8 +220,8 @@ worker_thread (void *thread_data_vp)
+       }
+     }
+ 
+-    if (DEBUG_PARALLEL)
+-      printf ("thread retiring domain %zu\n", i);
++    if (thread_data->verbose)
++      printf ("thread %zu retiring domain %zu\n", thread_data->thread_num, i);
+ 
+     /* Retire domain. */
+     printf ("%s", output);
+@@ -227,8 +237,8 @@ worker_thread (void *thread_data_vp)
+     }
+   }
+ 
+-  if (DEBUG_PARALLEL)
+-    printf ("thread exiting\n");
++  if (thread_data->verbose)
++    printf ("thread %zu exiting\n", thread_data->thread_num);
+ 
+   return &thread_data->r;
+ }
+-- 
+1.8.3.1
+
diff --git a/libguestfs.spec b/libguestfs.spec
index 76e31c5..8e72936 100644
--- a/libguestfs.spec
+++ b/libguestfs.spec
@@ -12,13 +12,15 @@ Summary:       Access and modify virtual machine disk images
 Name:          libguestfs
 Epoch:         1
 Version:       1.23.20
-Release:       4%{?dist}
+Release:       5%{?dist}
 License:       LGPLv2+
 
 # Source and patches.
 URL:           http://libguestfs.org/
 Source0:       http://libguestfs.org/download/1.23-development/%{name}-%{version}.tar.gz
 
+Patch1:        0001-virt-df-parallel-Compile-debugging-messages-in-alway.patch
+
 # Basic build requirements:
 BuildRequires: perl(Pod::Simple)
 BuildRequires: perl(Pod::Man)
@@ -558,6 +560,8 @@ for %{name}.
 %prep
 %setup -q
 
+%patch1 -p1
+
 if [ "$(getenforce | tr '[A-Z]' '[a-z]')" != "disabled" ]; then
     # For sVirt to work, the local temporary directory we use in the
     # tests must be labelled the same way as /tmp.
@@ -947,6 +951,10 @@ mkdir -p $RPM_BUILD_ROOT%{_localstatedir}/run/libguestfs
 
 
 %changelog
+* Tue Sep  3 2013 Richard W.M. Jones <rjones@redhat.com> - 1:1.23.20-5
+- Enable debugging messages in parallel virt-alignment-scan, virt-df
+  in order to debug possible race condition seen in Koji.
+
 * Mon Sep  2 2013 Richard W.M. Jones <rjones@redhat.com> - 1:1.23.20-4
 - Rebuild now that RHBZ#1003495 is supposed to be fixed.