diff --git a/src/workerd/api/data-url.c++ b/src/workerd/api/data-url.c++
index 5fa6a623d22..da1afae94bd 100644
--- a/src/workerd/api/data-url.c++
+++ b/src/workerd/api/data-url.c++
@@ -10,6 +10,18 @@ kj::Maybe<DataUrl> DataUrl::tryParse(kj::StringPtr url) {
   return kj::none;
 }
 
+static constexpr kj::FixedArray<uint8_t, 256> ascii_whitespace_table = []() consteval {
+  kj::FixedArray<uint8_t, 256> result{};
+  for (uint8_t c: {0x09, 0x0a, 0x0c, 0x0d, 0x20}) {
+    result[c] = true;
+  }
+  return result;
+}();
+
+constexpr bool isAsciiWhitespace(uint8_t c) noexcept {
+  return ascii_whitespace_table[c];
+}
+
 kj::Maybe<DataUrl> DataUrl::from(const jsg::Url& url) {
   if (url.getProtocol() != "data:"_kj) return kj::none;
   auto clone = url.clone(jsg::Url::EquivalenceOption::IGNORE_FRAGMENTS);
@@ -21,11 +33,6 @@ kj::Maybe<DataUrl> DataUrl::from(const jsg::Url& url) {
   // Per the fetch spec, it doesn't matter if the comma is within a quoted
   // string value in the MIME type... which is fun.
 
-  static const auto isAsciiWhitespace = [](auto c) {
-    return c == 0x09 /* tab */ || c == 0x0a /* lf  */ || c == 0x0c /* ff  */ ||
-        c == 0x0d /* cr  */ || c == 0x20 /* sp  */;
-  };
-
   static const auto trim = [](auto label) {
     size_t start = 0;
     auto end = label.size();
diff --git a/src/workerd/api/form-data.c++ b/src/workerd/api/form-data.c++
index 75cc8fad68c..7c209e138d0 100644
--- a/src/workerd/api/form-data.c++
+++ b/src/workerd/api/form-data.c++
@@ -86,11 +86,11 @@ void parseFormData(kj::Maybe<jsg::Lock&> js,
   const auto done = [](kj::ArrayPtr<const char>& body) {
     // Consume any (CR)LF characters that trailed the boundary and indicate continuation, or consume
     // the terminal "--" characters and indicate termination, or throw an error.
-    if (startsWith(body, "\n")) {
+    if (startsWith(body, "\n"_kj)) {
       body = body.slice(1, body.size());
-    } else if (startsWith(body, "\r\n")) {
+    } else if (startsWith(body, "\r\n"_kj)) {
       body = body.slice(2, body.size());
-    } else if (startsWith(body, "--")) {
+    } else if (startsWith(body, "--"_kj)) {
       // We're done!
       return true;
     } else {
diff --git a/src/workerd/util/mimetype.c++ b/src/workerd/util/mimetype.c++
index 495cc85442c..c33414307e8 100644
--- a/src/workerd/util/mimetype.c++
+++ b/src/workerd/util/mimetype.c++
@@ -6,7 +6,6 @@
 #include <kj/debug.h>
 #include <kj/string-tree.h>
 #include <workerd/util/string-buffer.h>
-#include <array>
 
 namespace workerd {
 
@@ -16,8 +15,8 @@ constexpr bool isWhitespace(const char c) noexcept {
   return (c == '\r' || c == '\n' || c == '\t' || c == ' ');
 }
 
-constexpr std::array<uint8_t, 256> token_table = []() consteval {
-  std::array<uint8_t, 256> result{};
+static constexpr kj::FixedArray<uint8_t, 256> token_table = []() consteval {
+  kj::FixedArray<uint8_t, 256> result{};
 
   for (uint8_t c:
       {'!', '#', '$', '%', '&', '\'', '*', '+', '\\', '-', '.', '^', '_', '`', '|', '~'}) {
@@ -46,8 +45,8 @@ constexpr bool isTokenChar(const uint8_t c) noexcept {
   return token_table[c];
 }
 
-constexpr std::array<uint8_t, 256> quoted_string_token_table = []() consteval {
-  std::array<uint8_t, 256> result{};
+static constexpr kj::FixedArray<uint8_t, 256> quoted_string_token_table = []() consteval {
+  kj::FixedArray<uint8_t, 256> result{};
   result['\t'] = true;
 
   for (uint8_t c = 0x20; c <= 0x7e; c++) {