diff --git a/core/fmt/fmt.odin b/core/fmt/fmt.odin
index 01d4ec26d..61060e194 100644
--- a/core/fmt/fmt.odin
+++ b/core/fmt/fmt.odin
@@ -994,6 +994,33 @@ _fmt_int :: proc(fi: ^Info, u: u64, base: int, is_signed: bool, bit_size: int, d
 		}
 	}
 
+	buf: [256]byte
+	start := 0
+
+	if fi.hash && !is_signed {
+		switch base {
+		case 2:
+			io.write_byte(fi.writer, '0', &fi.n)
+			io.write_byte(fi.writer, 'b', &fi.n)
+			start = 2
+
+		case 8:
+			io.write_byte(fi.writer, '0', &fi.n)
+			io.write_byte(fi.writer, 'o', &fi.n)
+			start = 2
+
+		case 12:
+			io.write_byte(fi.writer, '0', &fi.n)
+			io.write_byte(fi.writer, 'o', &fi.n)
+			start = 2
+
+		case 16:
+			io.write_byte(fi.writer, '0', &fi.n)
+			io.write_byte(fi.writer, 'x', &fi.n)
+			start = 2
+		}
+	}
+
 	prec := 0
 	if fi.prec_set {
 		prec = fi.prec
@@ -1019,14 +1046,10 @@ _fmt_int :: proc(fi: ^Info, u: u64, base: int, is_signed: bool, bit_size: int, d
 		panic("_fmt_int: unknown base, whoops")
 	}
 
-	buf: [256]byte
-	start := 0
-
 	flags: strconv.Int_Flags
-	if fi.hash { flags |= {.Prefix} }
-	if fi.plus { flags |= {.Plus}   }
+	if fi.hash && !fi.zero && start == 0 { flags |= {.Prefix} }
+	if fi.plus               { flags |= {.Plus}   }
 	s := strconv.append_bits(buf[start:], u, base, is_signed, bit_size, digits, flags)
-
 	prev_zero := fi.zero
 	defer fi.zero = prev_zero
 	fi.zero = false
@@ -1056,6 +1079,33 @@ _fmt_int_128 :: proc(fi: ^Info, u: u128, base: int, is_signed: bool, bit_size: i
 		}
 	}
 
+	buf: [256]byte
+	start := 0
+
+	if fi.hash && !is_signed {
+		switch base {
+		case 2:
+			io.write_byte(fi.writer, '0', &fi.n)
+			io.write_byte(fi.writer, 'b', &fi.n)
+			start = 2
+
+		case 8:
+			io.write_byte(fi.writer, '0', &fi.n)
+			io.write_byte(fi.writer, 'o', &fi.n)
+			start = 2
+
+		case 12:
+			io.write_byte(fi.writer, '0', &fi.n)
+			io.write_byte(fi.writer, 'o', &fi.n)
+			start = 2
+
+		case 16:
+			io.write_byte(fi.writer, '0', &fi.n)
+			io.write_byte(fi.writer, 'x', &fi.n)
+			start = 2
+		}
+	}
+
 	prec := 0
 	if fi.prec_set {
 		prec = fi.prec
@@ -1081,12 +1131,9 @@ _fmt_int_128 :: proc(fi: ^Info, u: u128, base: int, is_signed: bool, bit_size: i
 		panic("_fmt_int: unknown base, whoops")
 	}
 
-	buf: [256]byte
-	start := 0
-
 	flags: strconv.Int_Flags
-	if fi.hash && !fi.zero { flags |= {.Prefix} }
-	if fi.plus             { flags |= {.Plus}   }
+	if fi.hash && !fi.zero && start == 0 { flags |= {.Prefix} }
+	if fi.plus                           { flags |= {.Plus}   }
 	s := strconv.append_bits_128(buf[start:], u, base, is_signed, bit_size, digits, flags)
 
 	if fi.hash && fi.zero && fi.indent == 0 {