diff --git a/Modules/_struct.c b/Modules/_struct.c
index 3e0ab31..6a89d8c 100644
--- a/Modules/_struct.c
+++ b/Modules/_struct.c
@@ -1900,18 +1900,20 @@
 PyDoc_STRVAR(module_doc,
 "Functions to convert between Python values and C structs.\n\
 Python bytes objects are used to hold the data representing the C struct\n\
-and also as format strings to describe the layout of data in the C struct.\n\
+and also as format strings (explained below) to describe the layout of data\n\
+in the C struct.\n\
 \n\
 The optional first format char indicates byte order, size and alignment:\n\
- @: native order, size & alignment (default)\n\
- =: native order, std. size & alignment\n\
- <: little-endian, std. size & alignment\n\
- >: big-endian, std. size & alignment\n\
- !: same as >\n\
+  @: native order, size & alignment (default)\n\
+  =: native order, std. size & alignment\n\
+  <: little-endian, std. size & alignment\n\
+  >: big-endian, std. size & alignment\n\
+  !: same as >\n\
 \n\
 The remaining chars indicate types of args and must match exactly;\n\
 these can be preceded by a decimal repeat count:\n\
   x: pad byte (no data); c:char; b:signed byte; B:unsigned byte;\n\
+  ?: _Bool (requires C99; if not available, char is used instead)\n\
   h:short; H:unsigned short; i:int; I:unsigned int;\n\
   l:long; L:unsigned long; f:float; d:double.\n\
 Special cases (preceding decimal count indicates length):\n\