diff --git a/block.c b/block.c
index 473eb6e..73029fa 100644
--- a/block.c
+++ b/block.c
@@ -5751,12 +5751,11 @@
         return;
     }
 
+    /* Create parameter list */
     create_opts = qemu_opts_append(create_opts, drv->create_opts);
     create_opts = qemu_opts_append(create_opts, proto_drv->create_opts);
 
-    /* Create parameter list with default values */
     opts = qemu_opts_create(create_opts, NULL, 0, &error_abort);
-    qemu_opt_set_number(opts, BLOCK_OPT_SIZE, img_size, &error_abort);
 
     /* Parse -o options */
     if (options) {
@@ -5766,6 +5765,13 @@
         }
     }
 
+    if (!qemu_opt_get(opts, BLOCK_OPT_SIZE)) {
+        qemu_opt_set_number(opts, BLOCK_OPT_SIZE, img_size, &error_abort);
+    } else if (img_size != UINT64_C(-1)) {
+        error_setg(errp, "The image size must be specified only once");
+        goto out;
+    }
+
     if (base_filename) {
         qemu_opt_set(opts, BLOCK_OPT_BACKING_FILE, base_filename, &local_err);
         if (local_err) {
diff --git a/tests/qemu-iotests/049 b/tests/qemu-iotests/049
index c100d30..051a1c7 100755
--- a/tests/qemu-iotests/049
+++ b/tests/qemu-iotests/049
@@ -78,6 +78,11 @@
     test_qemu_img create -f $IMGFMT -o size=$s "$TEST_IMG"
 done
 
+echo "== 4. Specify size twice (-o and traditional parameter) =="
+echo
+
+test_qemu_img create -f $IMGFMT -o size=10M "$TEST_IMG" 20M
+
 echo "== Check correct interpretation of suffixes for cluster size =="
 echo
 sizes="1024 1024b 1k 1K 1M "
diff --git a/tests/qemu-iotests/049.out b/tests/qemu-iotests/049.out
index 6b50540..affa55b 100644
--- a/tests/qemu-iotests/049.out
+++ b/tests/qemu-iotests/049.out
@@ -121,6 +121,11 @@
 Optional suffix k, M, G, T, P or E means kilo-, mega-, giga-, tera-, peta-
 and exabytes, respectively.
 
+== 4. Specify size twice (-o and traditional parameter) ==
+
+qemu-img create -f qcow2 -o size=10M TEST_DIR/t.qcow2 20M
+qemu-img: TEST_DIR/t.qcow2: The image size must be specified only once
+
 == Check correct interpretation of suffixes for cluster size ==
 
 qemu-img create -f qcow2 -o cluster_size=1024 TEST_DIR/t.qcow2 64M