diff --git a/daemon/lvm.c b/daemon/lvm.c
index 4026c4f92..9d91b6459 100644
--- a/daemon/lvm.c
+++ b/daemon/lvm.c
@@ -723,7 +723,18 @@ char *
 do_lvm_canonical_lv_name (const char *device)
 {
   char *canonical;
-  int r = lv_canonical (device, &canonical);
+  int r;
+
+  /* The device parameter is passed as PlainString because we can't
+   * really be sure that the device name will exist (especially for
+   * "/dev/mapper/..." names).  Do some sanity checking on it here.
+   */
+  if (!STRPREFIX (device, "/dev/")) {
+    reply_with_error ("%s: not a device name", device);
+    return NULL;
+  }
+
+  r = lv_canonical (device, &canonical);
   if (r == -1)
     return NULL;
 
diff --git a/generator/actions_core.ml b/generator/actions_core.ml
index fba6c39ca..81cb99ea8 100644
--- a/generator/actions_core.ml
+++ b/generator/actions_core.ml
@@ -6002,7 +6002,7 @@ See also C<guestfs_pread>." };
 
   { defaults with
     name = "lvm_canonical_lv_name"; added = (1, 5, 24);
-    style = RString (RDevice, "lv"), [String (Device, "lvname")], [];
+    style = RString (RDevice, "lv"), [String (PlainString, "lvname")], [];
     tests = [
       InitBasicFSonLVM, IfAvailable "lvm2", TestResultString (
         [["lvm_canonical_lv_name"; "/dev/mapper/VG-LV"]], "/dev/VG/LV"), [];