diff --git a/sys/vm/vm_phys.c b/sys/vm/vm_phys.c
index 5c33be43079c..4169f25b7e46 100644
--- a/sys/vm/vm_phys.c
+++ b/sys/vm/vm_phys.c
@@ -263,6 +263,7 @@ sysctl_vm_phys_free(SYSCTL_HANDLER_ARGS)
 			}
 		}
 	}
+	sbuf_putc(&sbuf, 0); /* nullterm */
 	error = sbuf_finish(&sbuf);
 	sbuf_delete(&sbuf);
 	return (error);
@@ -292,6 +293,7 @@ sysctl_vm_phys_segs(SYSCTL_HANDLER_ARGS)
 		sbuf_printf(&sbuf, "domain:    %d\n", seg->domain);
 		sbuf_printf(&sbuf, "free list: %p\n", seg->free_queues);
 	}
+	sbuf_putc(&sbuf, 0); /* nullterm */
 	error = sbuf_finish(&sbuf);
 	sbuf_delete(&sbuf);
 	return (error);
diff --git a/sys/vm/vm_reserv.c b/sys/vm/vm_reserv.c
index 585a7494060c..4619a397591f 100644
--- a/sys/vm/vm_reserv.c
+++ b/sys/vm/vm_reserv.c
@@ -261,6 +261,7 @@ sysctl_vm_reserv_partpopq(SYSCTL_HANDLER_ARGS)
 		sbuf_printf(&sbuf, "%5d: %6dK, %6d\n", level,
 		    unused_pages * ((int)PAGE_SIZE / 1024), counter);
 	}
+	sbuf_putc(&sbuf, 0); /* nullterm */
 	error = sbuf_finish(&sbuf);
 	sbuf_delete(&sbuf);
 	return (error);