diff --git a/fet.c b/fet.c
index 6e83311..ac4e663 100644
--- a/fet.c
+++ b/fet.c
@@ -758,6 +758,8 @@ int fet_readmem(device_t dev_base, address_t addr, uint8_t *buffer,
 	while (count > 1) {
 		int plen = count > 128 ? 128 : count;
 
+		plen &= ~0x1;
+
 		if (xfer(dev, C_READMEMORY, NULL, 0, 2, addr, plen) < 0) {
 			printc_err("fet: failed to read "
 				"from 0x%04x\n", addr);
@@ -799,6 +801,8 @@ int fet_writemem(device_t dev_base, address_t addr,
 		int plen = count > 128 ? 128 : count;
 		int ret;
 
+		plen &= ~0x1;
+
 		ret = xfer(dev, C_WRITEMEMORY, buffer, plen, 1, addr);
 
 		if (ret < 0) {