diff --git a/src/storage/storage_backend_rbd.c b/src/storage/storage_backend_rbd.c
index 3e70a42bb5..c9b47e215a 100644
--- a/src/storage/storage_backend_rbd.c
+++ b/src/storage/storage_backend_rbd.c
@@ -334,7 +334,7 @@ virStorageBackendRBDSetAllocation(virStorageVolDefPtr vol,
         goto cleanup;
     }
 
-    VIR_DEBUG("Found %zu bytes allocated for RBD image %s",
+    VIR_DEBUG("Found %llu bytes allocated for RBD image %s",
               allocation, vol->name);
 
     vol->target.allocation = allocation;