diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 80a21d86cf..6132674168 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -16866,6 +16866,11 @@ qemuDomainBlockCopy(virDomainPtr dom, const char *disk, const char *destxml,
             }
             bandwidth = param->value.ul;
         } else if (STREQ(param->field, VIR_DOMAIN_BLOCK_COPY_GRANULARITY)) {
+            if (param->value.ui != VIR_ROUND_UP_POWER_OF_TWO(param->value.ui)) {
+                virReportError(VIR_ERR_INVALID_ARG, "%s",
+                               _("granularity must be power of 2"));
+                goto cleanup;
+            }
             granularity = param->value.ui;
         } else if (STREQ(param->field, VIR_DOMAIN_BLOCK_COPY_BUF_SIZE)) {
             buf_size = param->value.ul;
diff --git a/tools/virsh.pod b/tools/virsh.pod
index 63325ffd73..5d52761ede 100644
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -1039,10 +1039,10 @@ unlimited, but more likely would overflow; it is safer to use 0 for that
 purpose.  Specifying I<granularity> allows fine-tuning of the granularity that
 will be copied when a dirty region is detected; larger values trigger less
 I/O overhead but may end up copying more data overall (the default value is
-usually correct); this value must be a power of two.  Specifying I<buf-size>
-will control how much data can be simultaneously in-flight during the copy;
-larger values use more memory but may allow faster completion (the default
-value is usually correct).
+usually correct); hypervisors may restrict this to be a power of two or fall
+within a certain range. Specifying I<buf-size> will control how much data can
+be simultaneously in-flight during the copy; larger values use more memory but
+may allow faster completion (the default value is usually correct).
 
 =item B<blockpull> I<domain> I<path> [I<bandwidth>] [I<base>]
 [I<--wait> [I<--verbose>] [I<--timeout> B<seconds>] [I<--async>]]