Index: head/lib/libkvm/kvm.c
===================================================================
--- head/lib/libkvm/kvm.c
+++ head/lib/libkvm/kvm.c
@@ -66,9 +66,14 @@
 
 SET_DECLARE(kvm_arch, struct kvm_arch);
 
+static char _kd_is_null[] = "";
+
 char *
 kvm_geterr(kvm_t *kd)
 {
+
+	if (kd == NULL)
+		return (_kd_is_null);
 	return (kd->errbuf);
 }
 
Index: head/lib/libkvm/kvm_geterr.3
===================================================================
--- head/lib/libkvm/kvm_geterr.3
+++ head/lib/libkvm/kvm_geterr.3
@@ -32,7 +32,7 @@
 .\"     @(#)kvm_geterr.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd June 4, 1993
+.Dd March 21, 2017
 .Dt KVM_GETERR 3
 .Os
 .Sh NAME
@@ -54,6 +54,15 @@
 The string returned is stored in memory owned by
 .Xr kvm 3
 so the message should be copied out and saved elsewhere if necessary.
+.Sh RETURN VALUES
+The function
+.Fn kvm_geterr
+will return "" if
+.Fa kd
+is
+.Dv NULL
+or an error has not been captured for
+.Fa kd .
 .Sh SEE ALSO
 .Xr kvm 3 ,
 .Xr kvm_close 3 ,