diff --git a/core/string/ustring.cpp b/core/string/ustring.cpp
index 637394324e9..1ab3219ccf4 100644
--- a/core/string/ustring.cpp
+++ b/core/string/ustring.cpp
@@ -111,10 +111,6 @@ Char16String &Char16String::operator+=(char16_t p_char) {
 	return *this;
 }
 
-void Char16String::operator=(const char16_t *p_cstr) {
-	copy_from(p_cstr);
-}
-
 const char16_t *Char16String::get_data() const {
 	if (size()) {
 		return &operator[](0);
@@ -123,27 +119,19 @@ const char16_t *Char16String::get_data() const {
 	}
 }
 
-void Char16String::copy_from(const char16_t *p_cstr) {
-	if (!p_cstr) {
+Error Char16String::copy_from(const StrRange<char16_t> &p_cstr) {
+	if (p_cstr.len == 0) {
 		resize(0);
-		return;
+		return OK;
 	}
 
-	const char16_t *s = p_cstr;
-	for (; *s; s++) {
-	}
-	size_t len = s - p_cstr;
+	const Error err = resize(p_cstr.len + 1); // Include terminating null char.
+	ERR_FAIL_COND_V_MSG(err != OK, err, "Failed to copy char16_t string.");
 
-	if (len == 0) {
-		resize(0);
-		return;
-	}
-
-	Error err = resize(++len); // include terminating null char
-
-	ERR_FAIL_COND_MSG(err != OK, "Failed to copy char16_t string.");
-
-	memcpy(ptrw(), p_cstr, len * sizeof(char16_t));
+	char16_t *dst = ptrw();
+	memcpy(dst, p_cstr.c_str, p_cstr.len * sizeof(char16_t));
+	dst[p_cstr.len] = _null;
+	return OK;
 }
 
 /*************************************************************************/
@@ -181,10 +169,6 @@ CharString &CharString::operator+=(char p_char) {
 	return *this;
 }
 
-void CharString::operator=(const char *p_cstr) {
-	copy_from(p_cstr);
-}
-
 const char *CharString::get_data() const {
 	if (size()) {
 		return &operator[](0);
@@ -193,24 +177,19 @@ const char *CharString::get_data() const {
 	}
 }
 
-void CharString::copy_from(const char *p_cstr) {
-	if (!p_cstr) {
+Error CharString::copy_from(const StrRange<char> &p_cstr) {
+	if (p_cstr.len == 0) {
 		resize(0);
-		return;
+		return OK;
 	}
 
-	size_t len = strlen(p_cstr);
+	const Error err = resize(p_cstr.len + 1); // Include terminating null char.
+	ERR_FAIL_COND_V_MSG(err != OK, err, "Failed to copy C-string.");
 
-	if (len == 0) {
-		resize(0);
-		return;
-	}
-
-	Error err = resize(++len); // include terminating null char
-
-	ERR_FAIL_COND_MSG(err != OK, "Failed to copy C-string.");
-
-	memcpy(ptrw(), p_cstr, len);
+	char *dst = ptrw();
+	memcpy(dst, p_cstr.c_str, p_cstr.len);
+	dst[p_cstr.len] = _null;
+	return OK;
 }
 
 /*************************************************************************/
diff --git a/core/string/ustring.h b/core/string/ustring.h
index b8ebeb99d7c..252fdfb6ab0 100644
--- a/core/string/ustring.h
+++ b/core/string/ustring.h
@@ -197,9 +197,9 @@ public:
 			_cowdata(std::move(p_str._cowdata)) {}
 	_FORCE_INLINE_ void operator=(const Char16String &p_str) { _cowdata._ref(p_str._cowdata); }
 	_FORCE_INLINE_ void operator=(Char16String &&p_str) { _cowdata = std::move(p_str._cowdata); }
-	_FORCE_INLINE_ Char16String(const char16_t *p_cstr) { copy_from(p_cstr); }
+	_FORCE_INLINE_ Char16String(const char16_t *p_cstr) { copy_from(StrRange<char16_t>::from_c_str(p_cstr)); }
 
-	void operator=(const char16_t *p_cstr);
+	void operator=(const char16_t *p_cstr) { copy_from(StrRange<char16_t>::from_c_str(p_cstr)); }
 	bool operator<(const Char16String &p_right) const;
 	Char16String &operator+=(char16_t p_char);
 	int length() const { return size() ? size() - 1 : 0; }
@@ -208,7 +208,7 @@ public:
 	explicit operator StrRange<char16_t>() const { return StrRange(get_data(), length()); }
 
 protected:
-	void copy_from(const char16_t *p_cstr);
+	Error copy_from(const StrRange<char16_t> &p_cstr);
 };
 
 /*************************************************************************/
@@ -242,9 +242,9 @@ public:
 			_cowdata(std::move(p_str._cowdata)) {}
 	_FORCE_INLINE_ void operator=(const CharString &p_str) { _cowdata._ref(p_str._cowdata); }
 	_FORCE_INLINE_ void operator=(CharString &&p_str) { _cowdata = std::move(p_str._cowdata); }
-	_FORCE_INLINE_ CharString(const char *p_cstr) { copy_from(p_cstr); }
+	_FORCE_INLINE_ CharString(const char *p_cstr) { copy_from(StrRange<char>::from_c_str(p_cstr)); }
 
-	void operator=(const char *p_cstr);
+	void operator=(const char *p_cstr) { copy_from(StrRange<char>::from_c_str(p_cstr)); }
 	bool operator<(const CharString &p_right) const;
 	bool operator==(const CharString &p_right) const;
 	CharString &operator+=(char p_char);
@@ -254,7 +254,7 @@ public:
 	explicit operator StrRange<char>() const { return StrRange(get_data(), length()); }
 
 protected:
-	void copy_from(const char *p_cstr);
+	Error copy_from(const StrRange<char> &p_cstr);
 };
 
 /*************************************************************************/