diff --git a/man2/pidfd_send_signal.2 b/man2/pidfd_send_signal.2
index ae754e30b..3715774a9 100644
--- a/man2/pidfd_send_signal.2
+++ b/man2/pidfd_send_signal.2
@@ -27,6 +27,8 @@
 pidfd_send_signal \- send a signal to a process specified by a file descriptor
 .SH SYNOPSIS
 .nf
+.B "#include <signal.h>"
+.PP
 .BI "int pidfd_send_signal(int " pidfd ", int " sig ", siginfo_t " info ,
 .BI "                      unsigned int " flags );
 .fi
@@ -122,7 +124,8 @@ is invalid (see
 .BR rt_sigqueueinfo (2)).
 .TP
 .B ESRCH
-The target process does not exist.
+The target process does not exist
+(i.e., it has terminated and been waited on).
 .SH VERSIONS
 .BR pidfd_send_signal ()
 first appeared in Linux 5.1.