diff --git a/src/storage/storage_backend_disk.c b/src/storage/storage_backend_disk.c
index 6394dac255994be0983312b850bdf6666013f2cb..4dc63d753e1e06ed6b305cad2466ac1f1d72f144 100644
--- a/src/storage/storage_backend_disk.c
+++ b/src/storage/storage_backend_disk.c
@@ -413,8 +413,8 @@ virStorageBackendDiskFindLabel(const char* device)
     /* if parted succeeds we have a valid partition table */
     ret = virCommandRun(cmd, NULL);
     if (ret < 0) {
-        if (strstr(output, "unrecognised disk label") ||
-            strstr(error, "unrecognised disk label")) {
+        if ((output && strstr(output, "unrecognised disk label")) ||
+            (error && strstr(error, "unrecognised disk label"))) {
             ret = 1;
         }
     }