diff --git a/src/target/jtag_scan.h b/src/target/jtag_scan.h
index 8aca96f588c..b6ac66cb2b5 100644
--- a/src/target/jtag_scan.h
+++ b/src/target/jtag_scan.h
@@ -27,7 +27,7 @@
 #include "jtagtap.h"
 
 #define JTAG_MAX_DEVS   32U
-#define JTAG_MAX_IR_LEN 38U
+#define JTAG_MAX_IR_LEN 32U /* NOTE: This is not long enough for all Xilinx devices */
 
 typedef struct jtag_dev {
 	uint32_t jd_idcode;