diff --git a/src/core/string_builder.cpp b/src/core/string_builder.cpp
index 3144656e4c..6ded799c30 100644
--- a/src/core/string_builder.cpp
+++ b/src/core/string_builder.cpp
@@ -113,13 +113,13 @@ void BaseStringBuilder::PutChar(char c)
 void BaseStringBuilder::PutUtf8(char32_t c)
 {
 	auto [buf, len] = EncodeUtf8(c);
-	this->PutBuffer(buf, len);
+	this->PutBuffer({buf, len});
 }
 
 /**
  * Append buffer.
  */
-void StringBuilder::PutBuffer(const char *str, size_type len)
+void StringBuilder::PutBuffer(std::span<const char> str)
 {
-	this->dest->append(str, len);
+	this->dest->append(str.data(), str.size());
 }
diff --git a/src/core/string_builder.hpp b/src/core/string_builder.hpp
index c6058bab05..24247c0c4a 100644
--- a/src/core/string_builder.hpp
+++ b/src/core/string_builder.hpp
@@ -26,17 +26,12 @@ public:
 	/**
 	 * Append buffer.
 	 */
-	virtual void PutBuffer(const char *str, size_type len) = 0;
-
-	/**
-	 * Append span.
-	 */
-	void PutBuffer(std::span<const char> str) { this->PutBuffer(str.data(), str.size()); }
+	virtual void PutBuffer(std::span<const char> str) = 0;
 
 	/**
 	 * Append string.
 	 */
-	void Put(std::string_view str) { this->PutBuffer(str.data(), str.size()); }
+	void Put(std::string_view str) { this->PutBuffer(str); }
 
 	void PutUint8(uint8_t value);
 	void PutSint8(int8_t value);
@@ -60,7 +55,7 @@ public:
 		auto result = std::to_chars(buf.data(), buf.data() + buf.size(), value, base);
 		if (result.ec != std::errc{}) return;
 		size_type len = result.ptr - buf.data();
-		this->PutBuffer(buf.data(), len);
+		this->PutBuffer({buf.data(), len});
 	}
 };
 
@@ -93,8 +88,7 @@ public:
 	 */
 	[[nodiscard]] std::string &GetString() noexcept { return *dest; }
 
-	using BaseStringBuilder::PutBuffer;
-	void PutBuffer(const char *str, size_type len) override;
+	void PutBuffer(std::span<const char> str) override;
 
 	/**
 	 * Append string.
diff --git a/src/core/string_inplace.cpp b/src/core/string_inplace.cpp
index 248fe8d130..1c3a5c8485 100644
--- a/src/core/string_inplace.cpp
+++ b/src/core/string_inplace.cpp
@@ -32,12 +32,12 @@
 /**
  * Append buffer.
  */
-void InPlaceBuilder::PutBuffer(const char *str, size_type len)
+void InPlaceBuilder::PutBuffer(std::span<const char> str)
 {
 	auto unused = this->GetBytesUnused();
-	if (len > unused) NOT_REACHED();
-	std::copy(str, str + len, this->dest.data() + this->position);
-	this->position += len;
+	if (str.size() > unused) NOT_REACHED();
+	std::ranges::copy(str, this->dest.data() + this->position);
+	this->position += str.size();
 }
 
 /**
diff --git a/src/core/string_inplace.hpp b/src/core/string_inplace.hpp
index eaf16752b0..5b97735291 100644
--- a/src/core/string_inplace.hpp
+++ b/src/core/string_inplace.hpp
@@ -47,8 +47,7 @@ public:
 	[[nodiscard]] bool AnyBytesUnused() const noexcept;
 	[[nodiscard]] size_type GetBytesUnused() const noexcept;
 
-	using BaseStringBuilder::PutBuffer;
-	void PutBuffer(const char *str, size_type len) override;
+	void PutBuffer(std::span<const char> str) override;
 
 	/**
 	 * Implementation of std::back_insert_iterator for non-growing destination buffer.