diff --git a/tests/misc/oracle/pp_bin_hex.res.oracle b/tests/misc/oracle/pp_bin_hex.res.oracle
index d01369b772004608d8fd69234102a43a5f103634..4791a522a343769216bd7ce7e105707e34f739e4 100644
--- a/tests/misc/oracle/pp_bin_hex.res.oracle
+++ b/tests/misc/oracle/pp_bin_hex.res.oracle
@@ -1,86 +1,86 @@
 --------------------------------------------------
 Dec. 0
 Hex. 0x0000
-Bin. 0b00000000
+Bin. 0b0000_0000
 --------------------------------------------------
 Dec. 1
 Hex. 0x0001
-Bin. 0b00000001
+Bin. 0b0000_0001
 --------------------------------------------------
 Dec. -1
 Hex. 1xFFFF
-Bin. 1b11111111
+Bin. 1b1111_1111
 --------------------------------------------------
 Dec. 2
 Hex. 0x0002
-Bin. 0b00000010
+Bin. 0b0000_0010
 --------------------------------------------------
 Dec. -2
 Hex. 1xFFFE
-Bin. 1b11111110
+Bin. 1b1111_1110
 --------------------------------------------------
 Dec. 5
 Hex. 0x0005
-Bin. 0b00000101
+Bin. 0b0000_0101
 --------------------------------------------------
 Dec. -5
 Hex. 1xFFFB
-Bin. 1b11111011
+Bin. 1b1111_1011
 --------------------------------------------------
 Dec. 9
 Hex. 0x0009
-Bin. 0b00001001
+Bin. 0b0000_1001
 --------------------------------------------------
 Dec. -9
 Hex. 1xFFF7
-Bin. 1b11110111
+Bin. 1b1111_0111
 --------------------------------------------------
 Dec. 16
 Hex. 0x0010
-Bin. 0b00010000
+Bin. 0b0001_0000
 --------------------------------------------------
 Dec. -16
 Hex. 1xFFF0
-Bin. 1b11110000
+Bin. 1b1111_0000
 --------------------------------------------------
 Dec. 127
 Hex. 0x007F
-Bin. 0b01111111
+Bin. 0b0111_1111
 --------------------------------------------------
 Dec. -127
 Hex. 1xFF81
-Bin. 1b10000001
+Bin. 1b1000_0001
 --------------------------------------------------
 Dec. 128
 Hex. 0x0080
-Bin. 0b10000000
+Bin. 0b1000_0000
 --------------------------------------------------
 Dec. -128
 Hex. 1xFF80
-Bin. 1b10000000
+Bin. 1b1000_0000
 --------------------------------------------------
 Dec. 255
 Hex. 0x00FF
-Bin. 0b11111111
+Bin. 0b1111_1111
 --------------------------------------------------
 Dec. -255
 Hex. 1xFF01
-Bin. 1b00000001
+Bin. 1b0000_0001
 --------------------------------------------------
 Dec. 4279173135
-Hex. 0xFF0F000F
-Bin. 0b11111111000011110000000000001111
+Hex. 0xFF0F_000F
+Bin. 0b1111_1111_0000_1111_0000_0000_0000_1111
 --------------------------------------------------
 Dec. -4279173135
-Hex. 1x00F0FFF1
-Bin. 1b00000000111100001111111111110001
+Hex. 1x00F0_FFF1
+Bin. 1b0000_0000_1111_0000_1111_1111_1111_0001
 --------------------------------------------------
 Dec. 386334727
-Hex. 0x17070007
-Bin. 0b00010111000001110000000000000111
+Hex. 0x1707_0007
+Bin. 0b0001_0111_0000_0111_0000_0000_0000_0111
 --------------------------------------------------
 Dec. -386334727
-Hex. 1xE8F8FFF9
-Bin. 1b11101000111110001111111111111001
+Hex. 1xE8F8_FFF9
+Bin. 1b1110_1000_1111_1000_1111_1111_1111_1001
 --------------------------------------------------
 [kernel] Parsing tests/misc/pp_bin_hex.i (no preprocessing)
diff --git a/tests/misc/pp_bin_hex.ml b/tests/misc/pp_bin_hex.ml
index 719fdbeb26100ae0783eab99f176d1bbbac41c53..41ab2e6ab92ee1beef120983f3e307461ada4811 100644
--- a/tests/misc/pp_bin_hex.ml
+++ b/tests/misc/pp_bin_hex.ml
@@ -1,6 +1,6 @@
 let pp_dec fmt z = Integer.pretty ~hexa:false fmt z
-let pp_hex fmt z = Integer.pp_hex ~nbits:16 fmt z
-let pp_bin fmt z = Integer.pp_bin ~nbits:8  fmt z
+let pp_hex fmt z = Integer.pp_hex ~nbits:16 ~sep:"_" fmt z
+let pp_bin fmt z = Integer.pp_bin ~nbits:8  ~sep:"_" fmt z
 
 let hrule () =
   Format.printf "--------------------------------------------------@."