diff --git a/lib/std/math/round.zig b/lib/std/math/round.zig
index 7e1ee1ebd1..c948431a35 100644
--- a/lib/std/math/round.zig
+++ b/lib/std/math/round.zig
@@ -20,6 +20,10 @@ pub fn round(x: anytype) @TypeOf(x) {
         f32 => round32(x),
         f64 => round64(x),
         f128 => round128(x),
+
+        // TODO this is not correct for some targets
+        c_longdouble => @floatCast(c_longdouble, round128(x)),
+
         else => @compileError("round not implemented for " ++ @typeName(T)),
     };
 }
diff --git a/lib/std/special/c.zig b/lib/std/special/c.zig
index db1c56c536..326ca3a8a0 100644
--- a/lib/std/special/c.zig
+++ b/lib/std/special/c.zig
@@ -98,6 +98,7 @@ comptime {
 
     @export(round, .{ .name = "round", .linkage = .Strong });
     @export(roundf, .{ .name = "roundf", .linkage = .Strong });
+    @export(roundl, .{ .name = "roundl", .linkage = .Strong });
 
     @export(fmin, .{ .name = "fmin", .linkage = .Strong });
     @export(fminf, .{ .name = "fminf", .linkage = .Strong });
@@ -575,11 +576,18 @@ fn fabsf(a: f32) callconv(.C) f32 {
     return math.fabs(a);
 }
 
+fn roundf(a: f32) callconv(.C) f32 {
+    return math.round(a);
+}
+
 fn round(a: f64) callconv(.C) f64 {
     return math.round(a);
 }
 
-fn roundf(a: f32) callconv(.C) f32 {
+fn roundl(a: c_longdouble) callconv(.C) c_longdouble {
+    if (!long_double_is_f128) {
+        @panic("TODO implement this");
+    }
     return math.round(a);
 }