diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index da6ddff6cb..768b184794 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -475,7 +475,7 @@ qemuBuildIoEventFdStr(virBufferPtr buf,
 }
 
 #define QEMU_SERIAL_PARAM_ACCEPTED_CHARS \
-  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_ "
+  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_ .+"
 
 static int
 qemuSafeSerialParamValue(const char *value)
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-disk-serial.args b/tests/qemuxml2argvdata/qemuxml2argv-disk-serial.args
index 6f512352be..a44af97fb7 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-disk-serial.args
+++ b/tests/qemuxml2argvdata/qemuxml2argv-disk-serial.args
@@ -22,4 +22,7 @@ server,nowait \
 -drive 'file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-1,\
 serial=\ \ WD-WMAP9A966149' \
 -device ide-drive,bus=ide.0,unit=1,drive=drive-ide0-0-1,id=ide0-0-1 \
+-drive 'file=/dev/HostVG/AllSerialChars,format=raw,if=none,id=drive-ide0-0-2,\
+serial=abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_\ .+' \
+-device ide-drive,bus=ide.0,unit=2,drive=drive-ide0-0-2,id=ide0-0-2 \
 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-disk-serial.xml b/tests/qemuxml2argvdata/qemuxml2argv-disk-serial.xml
index 9c21443921..ccd78204bf 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-disk-serial.xml
+++ b/tests/qemuxml2argvdata/qemuxml2argv-disk-serial.xml
@@ -20,6 +20,12 @@
       <serial>  WD-WMAP9A966149</serial>
       <address type='drive' controller='0' bus='0' target='0' unit='1'/>
     </disk>
+    <disk type='block' device='disk'>
+      <source dev='/dev/HostVG/AllSerialChars'/>
+      <target dev='hdb' bus='ide'/>
+      <serial>abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_ .+</serial>
+      <address type='drive' controller='0' bus='0' target='0' unit='2'/>
+    </disk>
     <controller type='usb' index='0'/>
     <controller type='ide' index='0'/>
     <memballoon model='virtio'/>