diff --git a/src/bun.zig b/src/bun.zig
index 214f69b033..e1d24f5d8f 100644
--- a/src/bun.zig
+++ b/src/bun.zig
@@ -2139,7 +2139,7 @@ pub fn initArgv(allocator: std.mem.Allocator) !void {
         };
 
         const argvu16 = argvu16_ptr[0..@intCast(length)];
-        var out_argv = try allocator.alloc([:0]u8, @intCast(length));
+        const out_argv = try allocator.alloc([:0]u8, @intCast(length));
         var string_builder = StringBuilder{};
 
         for (argvu16) |argraw| {
@@ -2149,11 +2149,12 @@ pub fn initArgv(allocator: std.mem.Allocator) !void {
 
         try string_builder.allocate(allocator);
 
-        for (argvu16, 0..) |argraw, i| {
+        for (argvu16, out_argv) |argraw, *out| {
             const arg = std.mem.span(argraw);
-            // Command line is expected to be valid UTF-16le so this never
-            // fails and it's okay to unwrap pointer
-            out_argv[i] = string_builder.append16(arg).?;
+
+            // Command line is expected to be valid UTF-16le
+            // ...but sometimes, it's not valid. https://github.com/oven-sh/bun/issues/11610
+            out.* = string_builder.append16(arg, default_allocator) orelse @panic("Failed to allocate memory for argv");
         }
 
         argv = out_argv;
diff --git a/src/string_builder.zig b/src/string_builder.zig
index c4c243d81d..60b46dbd32 100644
--- a/src/string_builder.zig
+++ b/src/string_builder.zig
@@ -48,20 +48,29 @@ pub fn count16(this: *StringBuilder, slice: []const u16) void {
 }
 
 pub fn count16Z(this: *StringBuilder, slice: [:0]const u16) void {
-    const result = bun.simdutf.length.utf8.from.utf16.le(slice);
+    const result = bun.strings.elementLengthUTF16IntoUTF8([:0]const u16, slice);
     this.cap += result + 1;
 }
 
-pub fn append16(this: *StringBuilder, slice: []const u16) ?[:0]u8 {
+pub fn append16(this: *StringBuilder, slice: []const u16, fallback_allocator: std.mem.Allocator) ?[:0]u8 {
     var buf = this.writable();
+    if (slice.len == 0) {
+        buf[0] = 0;
+        this.len += 1;
+        return buf[0..0 :0];
+    }
+
     const result = bun.simdutf.convert.utf16.to.utf8.with_errors.le(slice, buf);
     if (result.status == .success) {
         this.len += result.count + 1;
         buf[result.count] = 0;
         return buf[0..result.count :0];
+    } else {
+        var list = std.ArrayList(u8).init(fallback_allocator);
+        var out = bun.strings.toUTF8ListWithTypeBun(&list, []const u16, slice) catch return null;
+        out.append(0) catch return null;
+        return list.items[0 .. list.items.len - 1 :0];
     }
-
-    return null;
 }
 
 pub fn appendZ(this: *StringBuilder, slice: string) [:0]const u8 {