diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 75dc81a0a9..37f542a325 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -1694,7 +1694,7 @@ build-postgresql:
        <term><option>--with-segsize-blocks=SEGSIZE_BLOCKS</option></term>
        <listitem>
         <para>
-         Specify the segment size in blocks. If both
+         Specify the relation segment size in blocks. If both
          <option>--with-segsize</option> and this option are specified, this
          option wins.
 
@@ -3191,7 +3191,7 @@ ninja install
        <term><option>-Dsegsize_blocks=SEGSIZE_BLOCKS</option></term>
        <listitem>
         <para>
-         Specify the segment size in blocks. If both
+         Specify the relation segment size in blocks. If both
          <option>-Dsegsize</option> and this option are specified, this option
          wins.