diff --git a/rtl/ibex_compressed_decoder.sv b/rtl/ibex_compressed_decoder.sv
index 1a78da59..d0b31dd7 100644
--- a/rtl/ibex_compressed_decoder.sv
+++ b/rtl/ibex_compressed_decoder.sv
@@ -206,12 +206,14 @@ module ibex_compressed_decoder (
 
           3'b100: begin
             if (instr_i[12] == 1'b0) begin
-              // c.mv -> add rd/rs1, x0, rs2
-              instr_o = {7'b0, instr_i[6:2], 5'b0, 3'b0, instr_i[11:7], {OPCODE_OP}};
-
-              if (instr_i[6:2] == 5'b0) begin
+              if (instr_i[6:2] != 5'b0) begin
+                // c.mv -> add rd/rs1, x0, rs2
+                // (c.mv hints are translated into an add hint)
+                instr_o = {7'b0, instr_i[6:2], 5'b0, 3'b0, instr_i[11:7], {OPCODE_OP}};
+              end else begin
                 // c.jr -> jalr x0, rd/rs1, 0
                 instr_o = {12'b0, instr_i[11:7], 3'b0, 5'b0, {OPCODE_JALR}};
+                if (instr_i[11:7] == 5'b0)  illegal_instr_o = 1'b1;
               end
             end else begin
               if (instr_i[6:2] != 5'b0) begin