diff --git a/pipelined/src/uncore/gpio.sv b/pipelined/src/uncore/gpio.sv
index ad82e62a..a70b44db 100644
--- a/pipelined/src/uncore/gpio.sv
+++ b/pipelined/src/uncore/gpio.sv
@@ -146,8 +146,8 @@ module gpio (
 
   // chip i/o
   // connect OUT to IN for loopback testing
-  if (`GPIO_LOOPBACK_TEST) assign input0d = GPIOPinsOut & output_en | (GPIOPinsIn  & input_en);
-  else                     assign input0d = GPIOPinsIn  & input_en;
+  if (`GPIO_LOOPBACK_TEST) assign input0d = ((output_en & GPIOPinsOut) | (~output_en & GPIOPinsIn)) & input_en;
+  else                     assign input0d = GPIOPinsIn & input_en;
   flop #(32) sync1(HCLK,input0d,input1d);
   flop #(32) sync2(HCLK,input1d,input2d);
   flop #(32) sync3(HCLK,input2d,input3d);