diff --git a/disas/riscv.c b/disas/riscv.c
index 36609efdf5..b8ec546883 100644
--- a/disas/riscv.c
+++ b/disas/riscv.c
@@ -5084,26 +5084,10 @@ static bool check_constraints(rv_decode *dec, const rvc_constraint *c)
     return true;
 }
 
-/* instruction length */
-
+/* Same as insn_len() from target/riscv/internals.h */
 static size_t inst_length(rv_inst inst)
 {
-    /* NOTE: supports maximum instruction size of 64-bits */
-
-    /*
-     * instruction length coding
-     *
-     *      aa - 16 bit aa != 11
-     *   bbb11 - 32 bit bbb != 111
-     *  011111 - 48 bit
-     * 0111111 - 64 bit
-     */
-
-    return (inst &      0b11) != 0b11      ? 2
-         : (inst &   0b11100) != 0b11100   ? 4
-         : (inst &  0b111111) == 0b011111  ? 6
-         : (inst & 0b1111111) == 0b0111111 ? 8
-         : 0;
+    return (inst & 3) == 3 ? 4 : 2;
 }
 
 /* format instruction */