diff --git a/sys/dev/acpica/acpi_timer.c b/sys/dev/acpica/acpi_timer.c
index 67f47d9ed0c3..11c0e243e7c1 100644
--- a/sys/dev/acpica/acpi_timer.c
+++ b/sys/dev/acpica/acpi_timer.c
@@ -276,7 +276,7 @@ acpi_timer_sysctl_freq(SYSCTL_HANDLER_ARGS)
 }
  
 SYSCTL_PROC(_machdep, OID_AUTO, acpi_timer_freq, CTLTYPE_INT | CTLFLAG_RW,
-	    0, sizeof(u_int), acpi_timer_sysctl_freq, "I", "");
+    0, sizeof(u_int), acpi_timer_sysctl_freq, "I", "ACPI timer frequency");
 
 /*
  * Some ACPI timers are known or believed to suffer from implementation
diff --git a/sys/x86/isa/clock.c b/sys/x86/isa/clock.c
index 5556ee651a7f..388f6cf43174 100644
--- a/sys/x86/isa/clock.c
+++ b/sys/x86/isa/clock.c
@@ -527,7 +527,8 @@ sysctl_machdep_i8254_freq(SYSCTL_HANDLER_ARGS)
 }
 
 SYSCTL_PROC(_machdep, OID_AUTO, i8254_freq, CTLTYPE_INT | CTLFLAG_RW,
-    0, sizeof(u_int), sysctl_machdep_i8254_freq, "IU", "");
+    0, sizeof(u_int), sysctl_machdep_i8254_freq, "IU",
+    "i8254 timer frequency");
 
 static unsigned
 i8254_get_timecount(struct timecounter *tc)
diff --git a/sys/x86/x86/tsc.c b/sys/x86/x86/tsc.c
index 7aca10f4432e..04654d616ce6 100644
--- a/sys/x86/x86/tsc.c
+++ b/sys/x86/x86/tsc.c
@@ -361,7 +361,7 @@ sysctl_machdep_tsc_freq(SYSCTL_HANDLER_ARGS)
 }
 
 SYSCTL_PROC(_machdep, OID_AUTO, tsc_freq, CTLTYPE_U64 | CTLFLAG_RW,
-    0, 0, sysctl_machdep_tsc_freq, "QU", "");
+    0, 0, sysctl_machdep_tsc_freq, "QU", "Time Stamp Counter frequency");
 
 static unsigned
 tsc_get_timecount(struct timecounter *tc)