diff --git a/include/stdbool.h b/include/stdbool.h
index fad1c30801..d1c06ffe12 100755
--- a/include/stdbool.h
+++ b/include/stdbool.h
@@ -51,9 +51,14 @@
 
 /* bool, true, and false must be provided as macros so that they can be
  * redefined by the application if necessary.
+ *
+ * NOTE: Under C99 'bool' is required to be defined to be the intrinsic type
+ * _Bool.  However, in this NuttX context, we need backward compatibility
+ * to pre-C99 standards where _Bool is not an intrinsic type.  Hence, we
+ * use _Bool8 as the underlying type.
  */
 
-#define bool  _Bool
+#define bool  _Bool8
 #define true  1
 #define false 0
 
@@ -64,10 +69,17 @@
  ****************************************************************************/
 
 /* A byte is the smallest address memory element (at least in architectures
- * that do not support bit banding.  We select uint8_t versus the more standard
- * int as the underlying type to minimize the RAM footprint of the executable.
+ * that do not support bit banding).  The requirement is only that type _Bool
+ * be large enough to hold the values 0 and 1.  We select uint8_t to minimize
+ * the RAM footprint of the executable.
+ *
+ * NOTE: We can't actually define the type _Bool here.  Under C99 _Bool is
+ * an intrinsic type and cannot be the target of a typedef.  However, in this
+ * NuttX context, we also need backward compatibility to pre-C99 standards
+ * where _Bool is not an intrinsic type.  We work around this by using _Bool8
+ * as the underlying type.
  */
 
-typedef uint8_t _Bool;
+typedef uint8_t _Bool8;
 
 #endif /* __INCLUDE_STDBOOL_H */