diff --git a/flow.sh b/flow.sh
index 8a441ca..def150a 100755
--- a/flow.sh
+++ b/flow.sh
@@ -72,6 +72,7 @@ run_sims() {
 	printinfo "Start simulation"
 	cd "$FIFO_DIR"/sim
 	svutRun -f files.f -test async_fifo_unit_test.sv -sim icarus
+    svutRun -f files.f -test async_fifo_almost_threshold_test.sv -sim icarus
 	return $?
 }
 
diff --git a/rtl/rptr_empty.v b/rtl/rptr_empty.v
index c95f125..6263537 100644
--- a/rtl/rptr_empty.v
+++ b/rtl/rptr_empty.v
@@ -21,7 +21,7 @@ module rptr_empty
     );
 
     reg  [ADDRSIZE:0] rbin;
-    wire [ADDRSIZE:0] rgraynext, rbinnext, rgraynextm1;
+    wire [ADDRSIZE:0] rgraynext, rbinnext, rgraynextm1,rbinnextm1;
     wire              arempty_val, rempty_val;
 
     //-------------------
@@ -39,8 +39,9 @@ module rptr_empty
     // Memory read-address pointer (okay to use binary to address memory)
     assign raddr     = rbin[ADDRSIZE-1:0];
     assign rbinnext  = rbin + (rinc & ~rempty);
+    assign rbinnextm1 = rbin + (rinc & ~rempty) + AREMPTYSIZE;
     assign rgraynext = (rbinnext >> 1) ^ rbinnext;
-    assign rgraynextm1 = ((rbinnext + AREMPTYSIZE) >> 1) ^ (rbinnext + AREMPTYSIZE);
+    assign rgraynextm1 = (rbinnextm1 >> 1) ^ rbinnextm1;;
 
     //---------------------------------------------------------------
     // FIFO empty when the next rptr == synchronized wptr or on reset
diff --git a/rtl/wptr_full.v b/rtl/wptr_full.v
index 11158a0..a36b91e 100644
--- a/rtl/wptr_full.v
+++ b/rtl/wptr_full.v
@@ -21,7 +21,7 @@ module wptr_full
 	);
 
     reg  [ADDRSIZE:0] wbin;
-    wire [ADDRSIZE:0] wgraynext, wbinnext, wgraynextp1;
+    wire [ADDRSIZE:0] wgraynext, wbinnext, wgraynextp1,wbinnextp1;
     wire              awfull_val, wfull_val;
 
 	// GRAYSTYLE2 pointer
@@ -37,8 +37,9 @@ module wptr_full
     // Memory write-address pointer (okay to use binary to address memory)
     assign waddr = wbin[ADDRSIZE-1:0];
     assign wbinnext  = wbin + (winc & ~wfull);
+    assign wbinnextp1 = wbin + (winc & ~wfull) + AWFULLSIZE;
     assign wgraynext = (wbinnext >> 1) ^ wbinnext;
-    assign wgraynextp1 = ((wbinnext + AWFULLSIZE) >> 1) ^ (wbinnext + AWFULLSIZE);
+    assign wgraynextp1 = (wbinnextp1 >> 1) ^ wbinnextp1;
 
     //------------------------------------------------------------------
     // Simplified version of the three necessary full-tests:
diff --git a/sim/async_fifo_almost_threshold_test.sv b/sim/async_fifo_almost_threshold_test.sv
new file mode 100644
index 0000000..46c5052
--- /dev/null
+++ b/sim/async_fifo_almost_threshold_test.sv
@@ -0,0 +1,156 @@
+
+`include "svut_h.sv"
+`timescale 1 ns / 1 ps
+
+module async_fifo_unit_test;
+
+    `SVUT_SETUP
+
+    `ifndef AEMPTY
+    `define AEMPTY 1
+    `endif
+
+    `ifndef AFULL
+    `define AFULL 1
+    `endif
+
+    `ifndef FALLTHROUGH
+    `define FALLTHROUGH "TRUE"
+    `endif
+
+    parameter DSIZE = 16;
+    parameter ASIZE = 13;
+    parameter AREMPTYSIZE = `AEMPTY;
+    parameter AWFULLSIZE = 4096;
+    parameter FALLTHROUGH = `FALLTHROUGH;
+    parameter MAX_TRAFFIC = 10;
+
+    integer timeout;
+
+    reg              wclk;
+    reg              wrst_n;
+    reg              winc;
+    reg  [DSIZE-1:0] wdata;
+    wire             wfull;
+    wire             awfull;
+    reg              rclk;
+    reg              rrst_n;
+    reg              rinc;
+    wire [DSIZE-1:0] rdata;
+    wire             rempty;
+    wire             arempty;
+
+    async_fifo
+    #(
+        .DSIZE        (DSIZE),
+        .ASIZE        (ASIZE),
+        .AWFULLSIZE   (AWFULLSIZE),
+        .AREMPTYSIZE  (AREMPTYSIZE),
+        .FALLTHROUGH  (FALLTHROUGH)
+    )
+    dut
+    (
+        wclk,
+        wrst_n,
+        winc,
+        wdata,
+        wfull,
+        awfull,
+        rclk,
+        rrst_n,
+        rinc,
+        rdata,
+        rempty,
+        arempty
+    );
+
+    // An example to create a clock
+    initial wclk = 1'b0;
+    always #2 wclk <= ~wclk;
+    initial rclk = 1'b0;
+    always #3 rclk <= ~rclk;
+
+    // An example to dump data for visualization
+    initial begin
+        $dumpfile("async_fifo_unit_test.vcd");
+        $dumpvars(0, async_fifo_unit_test);
+    end
+
+    task setup(msg="Setup testcase");
+    begin
+
+        wrst_n = 1'b0;
+        winc = 1'b0;
+        wdata = 0;
+        rrst_n = 1'b0;
+        rinc = 1'b0;
+        #100;
+        wrst_n = 1;
+        rrst_n = 1;
+        #50;
+        timeout = 0;
+        @(posedge wclk);
+
+    end
+    endtask
+
+    task teardown(msg="Tearing down");
+    begin
+        #50;
+    end
+    endtask
+
+    `TEST_SUITE("ASYNCFIFO")
+
+    `UNIT_TEST("TEST_IDLE")
+
+        `FAIL_IF(wfull);
+        `FAIL_IF(!rempty);
+
+    `UNIT_TEST_END
+
+
+    `UNIT_TEST("TEST_MULTIPLE_WRITE_THEN_READ")
+
+
+        // repeat for 3 times
+
+        for( int j = 0; j < 3; j= j+1)begin
+
+            // write 4096 data
+            winc = 1;
+            for (int i=0; i<(2**(ASIZE-1)); i=i+1) begin
+
+                @(negedge wclk)
+                wdata = i;
+
+            end
+
+            @(negedge wclk);
+            winc = 0;
+
+            @(posedge wclk)
+            `FAIL_IF_NOT_EQUAL(awfull, 1);
+
+
+            // try to read it
+            @(posedge rclk);
+
+            rinc = 1;
+            for (int i=0;  i<(2**(ASIZE-1)); i=i+1) begin
+                @(posedge rclk);
+                `FAIL_IF_NOT_EQUAL(rdata, i);
+            end
+            @(negedge rclk);
+            rinc = 0;
+
+            `FAIL_IF(rempty == 0);
+
+        end
+
+
+    `UNIT_TEST_END
+
+    `TEST_SUITE_END
+
+endmodule
\ No newline at end of file