diff --git a/opal/mca/btl/openib/btl_openib_component.c b/opal/mca/btl/openib/btl_openib_component.c
index 894ad1f7f1..1c5abaffcd 100644
--- a/opal/mca/btl/openib/btl_openib_component.c
+++ b/opal/mca/btl/openib/btl_openib_component.c
@@ -1509,6 +1509,9 @@ static uint64_t calculate_max_reg (const char *device_name)
         return (max_reg * 7) >> 3;
     }
 
+    /* Default to being able to register everything (to ensure that
+       max_reg is initialized in all cases) */
+    max_reg = mem_total;
     if (!strncmp(device_name, "mlx5", 4)) {
         max_reg = 2 * mem_total;