diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d15763234bee557810d518e2b0f931bf95245d8d..4585bf1b2df80d7295ce1cc5805cbc91945b23d5 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2006-04-03  Geoffrey Keating  <geoffk@apple.com>
+
+	* doc/extend.texi (Other Builtins): Document that
+	__builtin_nan is a compile-time constant only when its argument
+	is valid.
+
 2006-04-03  Adam Nemet  <anemet@caviumnetworks.com>
 
 	* simplify-rtx.c (simplify_unary_operation_1) <TRUNCATE>: When
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index cf1545826b906af24cfe481e0243d057a843beb8..ae3a7f2b8e3b5f40c9804c74b87a9aed3f31f221 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -5734,8 +5734,9 @@ is at the least significant bit of the significand.  The number is
 truncated to fit the significand field provided.  The significand is
 forced to be a quiet NaN@.
 
-This function, if given a string literal, is evaluated early enough
-that it is considered a compile-time constant.
+This function, if given a string literal all of which would have been
+consumed by strtol, is evaluated early enough that it is considered a
+compile-time constant.
 @end deftypefn
 
 @deftypefn {Built-in Function} _Decimal32 __builtin_nand32 (const char *str)