diff --git a/lib/std/mem.zig b/lib/std/mem.zig
index 4c198408b5..a6c4fe90be 100644
--- a/lib/std/mem.zig
+++ b/lib/std/mem.zig
@@ -232,6 +232,7 @@ test "Allocator alloc and remap with zero-bit type" {
 /// Copy all of source into dest at position 0.
 /// dest.len must be >= source.len.
 /// If the slices overlap, dest.ptr must be <= src.ptr.
+/// This function is deprecated; use @memmove instead.
 pub fn copyForwards(comptime T: type, dest: []T, source: []const T) void {
     for (dest[0..source.len], source) |*d, s| d.* = s;
 }
@@ -239,6 +240,7 @@ pub fn copyForwards(comptime T: type, dest: []T, source: []const T) void {
 /// Copy all of source into dest at position 0.
 /// dest.len must be >= source.len.
 /// If the slices overlap, dest.ptr must be >= src.ptr.
+/// This function is deprecated; use @memmove instead.
 pub fn copyBackwards(comptime T: type, dest: []T, source: []const T) void {
     // TODO instead of manually doing this check for the whole array
     // and turning off runtime safety, the compiler should detect loops like