diff --git a/riscu.md b/riscu.md
index 75267ebf..e4829ba6 100644
--- a/riscu.md
+++ b/riscu.md
@@ -58,4 +58,4 @@ The parameter `imm` denotes a signed integer value represented by a fixed number
 
 #### System
 
-`ecall`: system call number is in `a7`, parameters are in `a0-a2`, return value is in `a0`.
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+`ecall`: system call number is in `a7`, parameters are in `a0-a3`, return value is in `a0`.
\ No newline at end of file