diff --git a/Userland/Libraries/LibCrypto/ASN1/DER.cpp b/Userland/Libraries/LibCrypto/ASN1/DER.cpp
index 73e827bd68b..c7ad2d4e525 100644
--- a/Userland/Libraries/LibCrypto/ASN1/DER.cpp
+++ b/Userland/Libraries/LibCrypto/ASN1/DER.cpp
@@ -5,6 +5,7 @@
  */
 
 #include <AK/IntegralMath.h>
+#include <AK/Math.h>
 #include <AK/Stream.h>
 #include <AK/Try.h>
 #include <AK/Utf8View.h>
@@ -262,7 +263,8 @@ ErrorOr<void> Encoder::write_length(size_t value)
     if (value < 0x80)
         return write_byte(value);
 
-    size_t size_in_bits = AK::ceil_log2(value);
+    double minimum_bits = AK::log2(value);
+    size_t size_in_bits = AK::floor(minimum_bits) + 1;
     size_t size = ceil_div(size_in_bits, 8ul);
     TRY(write_byte(0x80 | size));