diff --git a/pw_fastboot/fastboot_device.cc b/pw_fastboot/fastboot_device.cc
index 380627876..0d0ff3d66 100644
--- a/pw_fastboot/fastboot_device.cc
+++ b/pw_fastboot/fastboot_device.cc
@@ -109,10 +109,10 @@ bool Device::HandleData(bool read, char* data, size_t size) {
     return false;
   }
   if (static_cast<size_t>(read_write_data_size) != size) {
-    PW_LOG_ERROR("%s expected %lu bytes, got %u",
+    PW_LOG_ERROR("%s expected %zu bytes, got %zu",
                  (read ? "read" : "write"),
-                 (long unsigned int)size,
-                 read_write_data_size);
+                 static_cast<size_t>(size),
+                 static_cast<size_t>(read_write_data_size));
     return false;
   }
   return true;
@@ -137,7 +137,7 @@ void Device::ExecuteCommands() {
 
     std::vector<std::string> args;
     std::string cmd_name;
-    if (cmd_name.starts_with("oem ")) {
+    if (stringutils::StartsWith(cmd_name, "oem ")) {
       args = {command};
       cmd_name = FB_CMD_OEM;
     } else {
diff --git a/pw_fastboot/lib/stringutils/public/stringutils/strings.h b/pw_fastboot/lib/stringutils/public/stringutils/strings.h
index 7cd26a137..cd29e0b20 100644
--- a/pw_fastboot/lib/stringutils/public/stringutils/strings.h
+++ b/pw_fastboot/lib/stringutils/public/stringutils/strings.h
@@ -85,4 +85,6 @@ bool ParseUint(const char* s, T* out, T max = std::numeric_limits<T>::max()) {
 std::string StringPrintf(const char* fmt, ...)
     __attribute__((__format__(FORMAT_ARCHETYPE, 1, 2)));
 
+bool StartsWith(std::string_view s, std::string_view prefix);
+
 }  // namespace stringutils
diff --git a/pw_fastboot/lib/stringutils/strings.cc b/pw_fastboot/lib/stringutils/strings.cc
index d33f85f74..d01f5f213 100644
--- a/pw_fastboot/lib/stringutils/strings.cc
+++ b/pw_fastboot/lib/stringutils/strings.cc
@@ -92,4 +92,8 @@ void StringAppendF(std::string* dst, const char* format, ...) {
   va_end(ap);
 }
 
+bool StartsWith(std::string_view s, std::string_view prefix) {
+  return s.substr(0, prefix.size()) == prefix;
+}
+
 }  // namespace stringutils
\ No newline at end of file