diff --git a/src/ieu/bmu/ext.sv b/src/ieu/bmu/ext.sv
index 05cb24c01..346b7811d 100644
--- a/src/ieu/bmu/ext.sv
+++ b/src/ieu/bmu/ext.sv
@@ -31,21 +31,17 @@
 `include "wally-config.vh"
 
 module ext #(parameter WIDTH = 32) (
-  input  logic [WIDTH-1:0] A, B,         // Operands
+  input  logic [WIDTH-1:0] A,            // Operands
+  input  logic [1:0] ExtSelect,          // B[2], B[0] of immediate
   output logic [WIDTH-1:0] ExtResult);   // Extend Result
 
   logic [WIDTH-1:0] sexthResult, zexthResult, sextbResult;
+
   assign sexthResult = {{(WIDTH-16){A[15]}},A[15:0]};
   assign zexthResult = {{(WIDTH-16){1'b0}},A[15:0]};
   assign sextbResult = {{(WIDTH-8){A[7]}},A[7:0]};
 
-  always_comb 
-    case({B[2],B[0]})
-      2'b00: ExtResult = zexthResult;
-      2'b10: ExtResult = sextbResult;
-      2'b11: ExtResult = sexthResult;
-      default: ExtResult = 0;
-    endcase
+  mux3 #(WIDTH) extmux(zexthResult, sextbResult, sexthResult, ExtSelect, ExtResult);
 
  
 endmodule
\ No newline at end of file
diff --git a/src/ieu/bmu/zbb.sv b/src/ieu/bmu/zbb.sv
index fc1918742..654146291 100644
--- a/src/ieu/bmu/zbb.sv
+++ b/src/ieu/bmu/zbb.sv
@@ -55,7 +55,7 @@ module zbb #(parameter WIDTH=32) (
 
   cnt #(WIDTH) cnt(.A(A), .RevA(RevA), .B(B[4:0]), .W64(W64), .CntResult(CntResult));
   byteUnit #(WIDTH) bu(.A(A), .ByteSelect(B[0]), .ByteResult(ByteResult));
-  ext #(WIDTH) ext(.A(A), .B(B), .ExtResult(ExtResult));
+  ext #(WIDTH) ext(.A(A), .ExtSelect({B[2], B[0]}), .ExtResult(ExtResult));
 
 
   assign MaxResult = (lt) ? B : A;