diff --git a/ChangeLog b/ChangeLog
index 831c876b6e..6be5c5d67b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2016-11-01  Joseph Myers  <joseph@codesourcery.com>
+
+	[BZ #19673]
+	* manual/math.texi (Exponents and Logarithms): Correct description
+	of clog10.
+
 2016-10-31  Carlos O'Donell  <carlos@redhat.com>
 
 	[Bz #20729]
diff --git a/manual/math.texi b/manual/math.texi
index ccafb949fe..b4bb32345e 100644
--- a/manual/math.texi
+++ b/manual/math.texi
@@ -804,10 +804,10 @@ These functions return the base 10 logarithm of the complex value
 @var{z}.  Mathematically, this corresponds to the value
 
 @ifnottex
-@math{log (z) = log10 (cabs (z)) + I * carg (z)}
+@math{log10 (z) = log10 (cabs (z)) + I * carg (z) / log (10)}
 @end ifnottex
 @tex
-$$\log_{10}(z) = \log_{10}|z| + i \arg z$$
+$$\log_{10}(z) = \log_{10}|z| + i \arg z / \log (10)$$
 @end tex
 
 These functions are GNU extensions.