Index: head/sys/dev/jedec_dimm/jedec_dimm.c
===================================================================
--- head/sys/dev/jedec_dimm/jedec_dimm.c
+++ head/sys/dev/jedec_dimm/jedec_dimm.c
@@ -795,7 +795,7 @@
 
 	/* If we're dealing with ASCII, convert trailing spaces to NULs. */
 	if (ascii) {
-		for (i = dstsz; i > 0; i--) {
+		for (i = dstsz - 1; i > 0; i--) {
 			if (dst[i] == ' ') {
 				dst[i] = 0;
 			} else if (dst[i] == 0) {