diff --git a/lib/human.c b/lib/human.c
index ab6b30d..d5d5a79 100644
--- a/lib/human.c
+++ b/lib/human.c
@@ -394,11 +394,20 @@ human_readable (uintmax_t n, char *buf, int opts,
 # define DEFAULT_BLOCK_SIZE 1024
 #endif
 
-static char const *const block_size_args[] = { "human-readable", "si", 0 };
+static char const *const block_size_args[] =
+  {
+    "human-readable",
+    "iec-iB",
+    "si",
+    "si-B",
+    0 };
+
 static int const block_size_opts[] =
   {
     human_autoscale + human_SI + human_base_1024,
-    human_autoscale + human_SI
+    human_autoscale + human_SI + human_base_1024 + human_B,
+    human_autoscale + human_SI,
+    human_autoscale + human_SI + human_B
   };
 
 static uintmax_t