diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig
index 9bf7075d28..c36b474de9 100644
--- a/lib/std/fmt.zig
+++ b/lib/std/fmt.zig
@@ -2297,6 +2297,7 @@ test "float.decimal" {
     try expectFmt("f64: 0.00030000", "f64: {d:.8}", .{@as(f64, 0.0003)});
     try expectFmt("f64: 0.00000", "f64: {d:.5}", .{@as(f64, 1.40130e-45)});
     try expectFmt("f64: 0.00000", "f64: {d:.5}", .{@as(f64, 9.999960e-40)});
+    try expectFmt("f64: 10000000000000.00", "f64: {d:.2}", .{@as(f64, 9999999999999.999)});
 }
 
 test "float.libc.sanity" {
diff --git a/lib/std/fmt/errol.zig b/lib/std/fmt/errol.zig
index e697b7d42f..e98c23f6ec 100644
--- a/lib/std/fmt/errol.zig
+++ b/lib/std/fmt/errol.zig
@@ -92,7 +92,10 @@ pub fn errol3(value: f64, buffer: []u8) FloatDecimal {
         };
     }
 
-    return errol3u(value, buffer);
+    // We generate digits starting at index 1. If rounding a buffer later then it may be
+    // required to generate a preceding digit in some cases (9.999) in which case we use
+    // the 0-index for this extra digit.
+    return errol3u(value, buffer[1..]);
 }
 
 /// Uncorrected Errol3 double to ASCII conversion.
@@ -162,11 +165,7 @@ fn errol3u(val: f64, buffer: []u8) FloatDecimal {
     }
 
     // digit generation
-
-    // We generate digits starting at index 1. If rounding a buffer later then it may be
-    // required to generate a preceding digit in some cases (9.999) in which case we use
-    // the 0-index for this extra digit.
-    var buf_index: usize = 1;
+    var buf_index: usize = 0;
     while (true) {
         var hdig = @floatToInt(u8, math.floor(high.val));
         if ((high.val == @intToFloat(f64, hdig)) and (high.off < 0)) hdig -= 1;
@@ -192,7 +191,7 @@ fn errol3u(val: f64, buffer: []u8) FloatDecimal {
     buf_index += 1;
 
     return FloatDecimal{
-        .digits = buffer[1..buf_index],
+        .digits = buffer[0..buf_index],
         .exp = exp,
     };
 }