diff --git a/man2/dup.2 b/man2/dup.2
index f90c7561b..6dc8058cd 100644
--- a/man2/dup.2
+++ b/man2/dup.2
@@ -45,7 +45,7 @@ dup, dup2, dup3 \- duplicate a file descriptor
 .BI "int dup2(int " oldfd ", int " newfd );
 .PP
 .BR "#define _GNU_SOURCE" "             /* See feature_test_macros(7) */"
-.BR "#include <fcntl.h>" "              /* Obtain O_* constant definitions */"
+.BR "#include <fcntl.h>" "              /* Definition of " O_* " constants */"
 .B #include <unistd.h>
 .PP
 .BI "int dup3(int " oldfd ", int " newfd ", int " flags );