diff --git a/src/freedreno/common/freedreno_pm4.h b/src/freedreno/common/freedreno_pm4.h
index 4320a5c8508..5a46c0a8124 100644
--- a/src/freedreno/common/freedreno_pm4.h
+++ b/src/freedreno/common/freedreno_pm4.h
@@ -71,6 +71,7 @@ pm4_pkt3_hdr(uint8_t opcode, uint16_t cnt)
 static inline uint32_t
 pm4_pkt4_hdr(uint16_t regindx, uint16_t cnt)
 {
+   assert(cnt < 0x7f);
    return CP_TYPE4_PKT | cnt | (pm4_odd_parity_bit(cnt) << 7) |
          ((regindx & 0x3ffff) << 8) |
          ((pm4_odd_parity_bit(regindx) << 27));