diff --git a/src/chrome.zig b/src/chrome.zig
index c58a4a4b939ac6d7ffbd8fb4e71966ce35f0a878..8cb2705ca95167df7e37e15071c324854f388e07 100644
--- a/src/chrome.zig
+++ b/src/chrome.zig
@@ -27,7 +27,7 @@ pub fn init_thread(args: struct { nfs.Dir }) !void {
     const dir = args[0];
     tid = linux.gettid();
 
-    path = try std.fmt.allocPrintZ(alloc, "trace.{d}.{d}.chrome.json", .{ pid, tid });
+    path = try nio.fmt.allocPrintZ(alloc, "trace.{d}.{d}.chrome.json", .{ pid, tid });
     file = try dir.createFile(path, .{});
     buffered_writer = .init(file);
 
diff --git a/src/spall.zig b/src/spall.zig
index 1ed28330f3084366d199950997adb45e840bc676..b5446d9747ee512caeeb2045f85d33d5ae3af71b 100644
--- a/src/spall.zig
+++ b/src/spall.zig
@@ -27,7 +27,7 @@ pub fn init_thread(args: struct { nfs.Dir }) !void {
     const dir = args[0];
     tid = linux.gettid();
 
-    path = try std.fmt.allocPrintZ(alloc, "{d}.{d}.spall", .{ pid, tid });
+    path = try nio.fmt.allocPrintZ(alloc, "{d}.{d}.spall", .{ pid, tid });
     file = try dir.createFile(path, .{});
     buffered_writer = .init(file);