diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index aa7b129b3b..b167949d9e 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -15437,10 +15437,15 @@ qemuDomainBlockCommit(virDomainPtr dom, const char *path, const char *base,
                                            VIR_DISK_CHAIN_READ_WRITE) < 0))
         goto endjob;
 
-    /* Start the commit operation.  */
+    /* Start the commit operation.  Pass the user's original spelling,
+     * if any, through to qemu, since qemu may behave differently
+     * depending on whether the input was specified as relative or
+     * absolute (that is, our absolute top_canon may do the wrong
+     * thing if the user specified a relative name). */
     qemuDomainObjEnterMonitor(driver, vm);
-    ret = qemuMonitorBlockCommit(priv->mon, device, top_canon, base_canon,
-                                 bandwidth);
+    ret = qemuMonitorBlockCommit(priv->mon, device,
+                                 top ? top : top_canon,
+                                 base ? base : base_canon, bandwidth);
     qemuDomainObjExitMonitor(driver, vm);
 
 endjob:
diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
index a2769dbe2b..e4707b7c05 100644
--- a/src/qemu/qemu_monitor.c
+++ b/src/qemu/qemu_monitor.c
@@ -1,7 +1,7 @@
 /*
  * qemu_monitor.c: interaction with QEMU monitor console
  *
- * Copyright (C) 2006-2013 Red Hat, Inc.
+ * Copyright (C) 2006-2014 Red Hat, Inc.
  * Copyright (C) 2006 Daniel P. Berrange
  *
  * This library is free software; you can redistribute it and/or
@@ -3188,7 +3188,7 @@ qemuMonitorBlockCommit(qemuMonitorPtr mon, const char *device,
     unsigned long long speed;
 
     VIR_DEBUG("mon=%p, device=%s, top=%s, base=%s, bandwidth=%ld",
-              mon, device, NULLSTR(top), NULLSTR(base), bandwidth);
+              mon, device, top, base, bandwidth);
 
     /* Convert bandwidth MiB to bytes - unfortunately the JSON QMP protocol is
      * limited to LLONG_MAX also for unsigned values */
diff --git a/src/qemu/qemu_monitor.h b/src/qemu/qemu_monitor.h
index eabf000969..7bb465bea9 100644
--- a/src/qemu/qemu_monitor.h
+++ b/src/qemu/qemu_monitor.h
@@ -647,7 +647,8 @@ int qemuMonitorBlockCommit(qemuMonitorPtr mon,
                            const char *top,
                            const char *base,
                            unsigned long bandwidth)
-    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(3);
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(3)
+    ATTRIBUTE_NONNULL(4);
 
 int qemuMonitorArbitraryCommand(qemuMonitorPtr mon,
                                 const char *cmd,
diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index 7d6b88b326..dbc04f68d2 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/src/qemu/qemu_monitor_json.c
@@ -3307,7 +3307,7 @@ qemuMonitorJSONBlockCommit(qemuMonitorPtr mon, const char *device,
                                      "s:device", device,
                                      "U:speed", speed,
                                      "s:top", top,
-                                     base ? "s:base" : NULL, base,
+                                     "s:base", base,
                                      NULL);
     if (!cmd)
         return -1;
diff --git a/src/qemu/qemu_monitor_json.h b/src/qemu/qemu_monitor_json.h
index a93c51eeb0..ef71588269 100644
--- a/src/qemu/qemu_monitor_json.h
+++ b/src/qemu/qemu_monitor_json.h
@@ -1,7 +1,7 @@
 /*
  * qemu_monitor_json.h: interaction with QEMU monitor console
  *
- * Copyright (C) 2006-2009, 2011-2013 Red Hat, Inc.
+ * Copyright (C) 2006-2009, 2011-2014 Red Hat, Inc.
  * Copyright (C) 2006 Daniel P. Berrange
  *
  * This library is free software; you can redistribute it and/or
@@ -258,7 +258,8 @@ int qemuMonitorJSONBlockCommit(qemuMonitorPtr mon,
                                const char *top,
                                const char *base,
                                unsigned long long bandwidth)
-    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(3);
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(3)
+    ATTRIBUTE_NONNULL(4);
 
 int qemuMonitorJSONArbitraryCommand(qemuMonitorPtr mon,
                                     const char *cmd_str,