diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
index 739fe61303..457cecdccb 100644
--- a/src/qemu/qemu_monitor.c
+++ b/src/qemu/qemu_monitor.c
@@ -3258,6 +3258,18 @@ qemuMonitorBlockCommit(qemuMonitorPtr mon, const char *device,
     return ret;
 }
 
+
+/* Probe whether active commits are supported by a given qemu binary. */
+bool
+qemuMonitorSupportsActiveCommit(qemuMonitorPtr mon)
+{
+    if (!mon->json)
+        return false;
+
+    return qemuMonitorJSONBlockCommit(mon, "bogus", NULL, NULL, 0) == -2;
+}
+
+
 /* Use the block-job-complete monitor command to pivot a block copy
  * job.  */
 int
diff --git a/src/qemu/qemu_monitor.h b/src/qemu/qemu_monitor.h
index 31b320498c..63e78d8e44 100644
--- a/src/qemu/qemu_monitor.h
+++ b/src/qemu/qemu_monitor.h
@@ -665,6 +665,7 @@ int qemuMonitorBlockCommit(qemuMonitorPtr mon,
                            unsigned long bandwidth)
     ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(3)
     ATTRIBUTE_NONNULL(4);
+bool qemuMonitorSupportsActiveCommit(qemuMonitorPtr mon);
 
 int qemuMonitorArbitraryCommand(qemuMonitorPtr mon,
                                 const char *cmd,
diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index 85168eb2ea..b5e8a20ef5 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/src/qemu/qemu_monitor_json.c
@@ -3454,7 +3454,14 @@ qemuMonitorJSONTransaction(qemuMonitorPtr mon, virJSONValuePtr actions)
     return ret;
 }
 
-/* speed is in bytes/sec */
+/* speed is in bytes/sec. Returns 0 on success, -1 with error message
+ * emitted on failure.
+ *
+ * Additionally, can be used to probe if active commit is supported:
+ * pass in a bogus device and NULL top and base.  The probe return is
+ * -2 if active commit is detected, -3 if inconclusive; with no error
+ * message issued.
+ */
 int
 qemuMonitorJSONBlockCommit(qemuMonitorPtr mon, const char *device,
                            const char *top, const char *base,
@@ -3467,14 +3474,30 @@ qemuMonitorJSONBlockCommit(qemuMonitorPtr mon, const char *device,
     cmd = qemuMonitorJSONMakeCommand("block-commit",
                                      "s:device", device,
                                      "U:speed", speed,
-                                     "s:top", top,
-                                     "s:base", base,
+                                     "S:top", top,
+                                     "S:base", base,
                                      NULL);
     if (!cmd)
         return -1;
 
     if ((ret = qemuMonitorJSONCommand(mon, cmd, &reply)) < 0)
         goto cleanup;
+    if (!top && !base) {
+        /* Normally we always specify top and base; but omitting them
+         * allows for probing whether qemu is new enough to support
+         * live commit.  */
+        if (qemuMonitorJSONHasError(reply, "DeviceNotFound")) {
+            VIR_DEBUG("block-commit supports active commit");
+            ret = -2;
+        } else {
+            /* This is a false negative for qemu 2.0; but probably not
+             * worth the additional complexity to worry about it */
+            VIR_DEBUG("block-commit requires 'top' parameter, "
+                      "assuming it lacks active commit");
+            ret = -3;
+        }
+        goto cleanup;
+    }
     ret = qemuMonitorJSONCheckError(cmd, reply);
 
  cleanup:
diff --git a/src/qemu/qemu_monitor_json.h b/src/qemu/qemu_monitor_json.h
index e29158e947..89e668cd7b 100644
--- a/src/qemu/qemu_monitor_json.h
+++ b/src/qemu/qemu_monitor_json.h
@@ -262,8 +262,7 @@ 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(4);
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
 
 int qemuMonitorJSONArbitraryCommand(qemuMonitorPtr mon,
                                     const char *cmd_str,
diff --git a/tests/qemumonitorjsontest.c b/tests/qemumonitorjsontest.c
index 2099dc874c..d136576ffc 100644
--- a/tests/qemumonitorjsontest.c
+++ b/tests/qemumonitorjsontest.c
@@ -1991,6 +1991,52 @@ testQemuMonitorJSONqemuMonitorJSONSendKeyHoldtime(const void *data)
     return ret;
 }
 
+static int
+testQemuMonitorJSONqemuMonitorSupportsActiveCommit(const void *data)
+{
+    virDomainXMLOptionPtr xmlopt = (virDomainXMLOptionPtr)data;
+    qemuMonitorTestPtr test = qemuMonitorTestNewSimple(true, xmlopt);
+    int ret = -1;
+    const char *error1 =
+        "{"
+        "  \"error\": {"
+        "    \"class\": \"DeviceNotFound\","
+        "    \"desc\": \"Device 'bogus' not found\""
+        "  }"
+        "}";
+    const char *error2 =
+        "{"
+        "  \"error\": {"
+        "    \"class\": \"GenericError\","
+        "    \"desc\": \"Parameter 'top' is missing\""
+        "  }"
+        "}";
+
+    if (!test)
+        return -1;
+
+    if (qemuMonitorTestAddItemParams(test, "block-commit", error1,
+                                     "device", "\"bogus\"",
+                                     NULL, NULL) < 0)
+        goto cleanup;
+
+    if (!qemuMonitorSupportsActiveCommit(qemuMonitorTestGetMonitor(test)))
+        goto cleanup;
+
+    if (qemuMonitorTestAddItemParams(test, "block-commit", error2,
+                                     "device", "\"bogus\"",
+                                     NULL, NULL) < 0)
+        goto cleanup;
+
+    if (qemuMonitorSupportsActiveCommit(qemuMonitorTestGetMonitor(test)))
+        goto cleanup;
+
+    ret = 0;
+ cleanup:
+    qemuMonitorTestFree(test);
+    return ret;
+}
+
 static int
 testQemuMonitorJSONqemuMonitorJSONGetDumpGuestMemoryCapability(const void *data)
 {
@@ -2263,6 +2309,7 @@ mymain(void)
     DO_TEST(qemuMonitorJSONSendKey);
     DO_TEST(qemuMonitorJSONGetDumpGuestMemoryCapability);
     DO_TEST(qemuMonitorJSONSendKeyHoldtime);
+    DO_TEST(qemuMonitorSupportsActiveCommit);
 
     DO_TEST_CPU_DATA("host");
     DO_TEST_CPU_DATA("full");