diff --git a/man2/s390_sthyi.2 b/man2/s390_sthyi.2
index d1abb17a4..acba43a20 100644
--- a/man2/s390_sthyi.2
+++ b/man2/s390_sthyi.2
@@ -27,6 +27,7 @@
 s390_sthyi \- emulate STHYI instruction
 .SH SYNOPSIS
 .nf
+.BR "#include <asm/sthyi.h>" "        /* Definition of " STHYI_* " constants */"
 .B #include <asm/unistd.h>
 .PP
 .BI "int s390_sthyi(unsigned long " function_code ", void *" resp_buffer ","
@@ -49,7 +50,7 @@ The
 argument indicates which function to perform.
 The following code(s) are supported:
 .TP
-0
+.B STHYI_FC_CP_IFL_CAP
 Return CP (Central Processor) and IFL (Integrated Facility for Linux)
 capacity information.
 .PP
@@ -58,7 +59,9 @@ The
 argument specifies the address of a response buffer.
 When the
 .I function_code
-is 0, the buffer must be one page (4K) in size.
+is
+.BR STHYI_FC_CP_IFL_CAP ,
+the buffer must be one page (4K) in size.
 If the system call returns 0,
 the response buffer will be filled with CPU capacity information.
 Otherwise, the response buffer's content is unchanged.