diff --git a/include/SFML/System/Utf.inl b/include/SFML/System/Utf.inl
index 7c9d2b69d..bca49243f 100644
--- a/include/SFML/System/Utf.inl
+++ b/include/SFML/System/Utf.inl
@@ -51,9 +51,13 @@ OutputIt priv::copy(InputIt first, InputIt last, OutputIt dFirst)
     return dFirst;
 }
 
+
+////////////////////////////////////////////////////////////
 template <typename In>
 In Utf<8>::decode(In begin, In end, char32_t& output, char32_t replacement)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     // clang-format off
     // Some useful precomputed data
     static constexpr std::array<std::uint8_t, 256> trailing =
@@ -158,6 +162,8 @@ Out Utf<8>::encode(char32_t input, Out output, std::uint8_t replacement)
 template <typename In>
 In Utf<8>::next(In begin, In end)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     char32_t codepoint = 0;
     return decode(begin, end, codepoint);
 }
@@ -167,6 +173,8 @@ In Utf<8>::next(In begin, In end)
 template <typename In>
 std::size_t Utf<8>::count(In begin, In end)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     std::size_t length = 0;
     while (begin != end)
     {
@@ -182,6 +190,8 @@ std::size_t Utf<8>::count(In begin, In end)
 template <typename In, typename Out>
 Out Utf<8>::fromAnsi(In begin, In end, Out output, const std::locale& locale)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     while (begin != end)
     {
         const char32_t codepoint = Utf<32>::decodeAnsi(*begin++, locale);
@@ -196,6 +206,8 @@ Out Utf<8>::fromAnsi(In begin, In end, Out output, const std::locale& locale)
 template <typename In, typename Out>
 Out Utf<8>::fromWide(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     while (begin != end)
     {
         char32_t codepoint = Utf<32>::decodeWide(*begin++);
@@ -210,6 +222,8 @@ Out Utf<8>::fromWide(In begin, In end, Out output)
 template <typename In, typename Out>
 Out Utf<8>::fromLatin1(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     // Latin-1 is directly compatible with Unicode encodings,
     // and can thus be treated as (a sub-range of) UTF-32
     while (begin != end)
@@ -223,6 +237,8 @@ Out Utf<8>::fromLatin1(In begin, In end, Out output)
 template <typename In, typename Out>
 Out Utf<8>::toAnsi(In begin, In end, Out output, char replacement, const std::locale& locale)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     while (begin != end)
     {
         char32_t codepoint = 0;
@@ -238,6 +254,8 @@ Out Utf<8>::toAnsi(In begin, In end, Out output, char replacement, const std::lo
 template <typename In, typename Out>
 Out Utf<8>::toWide(In begin, In end, Out output, wchar_t replacement)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     while (begin != end)
     {
         char32_t codepoint = 0;
@@ -253,6 +271,8 @@ Out Utf<8>::toWide(In begin, In end, Out output, wchar_t replacement)
 template <typename In, typename Out>
 Out Utf<8>::toLatin1(In begin, In end, Out output, char replacement)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     // Latin-1 is directly compatible with Unicode encodings,
     // and can thus be treated as (a sub-range of) UTF-32
     while (begin != end)
@@ -270,6 +290,8 @@ Out Utf<8>::toLatin1(In begin, In end, Out output, char replacement)
 template <typename In, typename Out>
 Out Utf<8>::toUtf8(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     return priv::copy(begin, end, output);
 }
 
@@ -278,6 +300,8 @@ Out Utf<8>::toUtf8(In begin, In end, Out output)
 template <typename In, typename Out>
 Out Utf<8>::toUtf16(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     while (begin != end)
     {
         char32_t codepoint = 0;
@@ -293,6 +317,8 @@ Out Utf<8>::toUtf16(In begin, In end, Out output)
 template <typename In, typename Out>
 Out Utf<8>::toUtf32(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     while (begin != end)
     {
         char32_t codepoint = 0;
@@ -308,6 +334,8 @@ Out Utf<8>::toUtf32(In begin, In end, Out output)
 template <typename In>
 In Utf<16>::decode(In begin, In end, char32_t& output, char32_t replacement)
 {
+    static_assert(sizeof(*begin) == 2, "Character type must be 2 bytes wide");
+
     const char16_t first = *begin++;
 
     // If it's a surrogate pair, first convert to a single UTF-32 character
@@ -385,6 +413,8 @@ Out Utf<16>::encode(char32_t input, Out output, char16_t replacement)
 template <typename In>
 In Utf<16>::next(In begin, In end)
 {
+    static_assert(sizeof(*begin) == 2, "Character type must be 2 bytes wide");
+
     char32_t codepoint = 0;
     return decode(begin, end, codepoint);
 }
@@ -394,6 +424,8 @@ In Utf<16>::next(In begin, In end)
 template <typename In>
 std::size_t Utf<16>::count(In begin, In end)
 {
+    static_assert(sizeof(*begin) == 2, "Character type must be 2 bytes wide");
+
     std::size_t length = 0;
     while (begin != end)
     {
@@ -409,6 +441,8 @@ std::size_t Utf<16>::count(In begin, In end)
 template <typename In, typename Out>
 Out Utf<16>::fromAnsi(In begin, In end, Out output, const std::locale& locale)
 {
+    static_assert(sizeof(*begin) == 2, "Character type must be 2 bytes wide");
+
     while (begin != end)
     {
         char32_t codepoint = Utf<32>::decodeAnsi(*begin++, locale);
@@ -423,6 +457,8 @@ Out Utf<16>::fromAnsi(In begin, In end, Out output, const std::locale& locale)
 template <typename In, typename Out>
 Out Utf<16>::fromWide(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 2, "Character type must be 2 bytes wide");
+
     while (begin != end)
     {
         char32_t codepoint = Utf<32>::decodeWide(*begin++);
@@ -437,6 +473,8 @@ Out Utf<16>::fromWide(In begin, In end, Out output)
 template <typename In, typename Out>
 Out Utf<16>::fromLatin1(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 2, "Character type must be 2 bytes wide");
+
     // Latin-1 is directly compatible with Unicode encodings,
     // and can thus be treated as (a sub-range of) UTF-32
     return priv::copy(begin, end, output);
@@ -447,6 +485,8 @@ Out Utf<16>::fromLatin1(In begin, In end, Out output)
 template <typename In, typename Out>
 Out Utf<16>::toAnsi(In begin, In end, Out output, char replacement, const std::locale& locale)
 {
+    static_assert(sizeof(*begin) == 2, "Character type must be 2 bytes wide");
+
     while (begin != end)
     {
         char32_t codepoint = 0;
@@ -462,6 +502,8 @@ Out Utf<16>::toAnsi(In begin, In end, Out output, char replacement, const std::l
 template <typename In, typename Out>
 Out Utf<16>::toWide(In begin, In end, Out output, wchar_t replacement)
 {
+    static_assert(sizeof(*begin) == 2, "Character type must be 2 bytes wide");
+
     while (begin != end)
     {
         char32_t codepoint = 0;
@@ -477,6 +519,8 @@ Out Utf<16>::toWide(In begin, In end, Out output, wchar_t replacement)
 template <typename In, typename Out>
 Out Utf<16>::toLatin1(In begin, In end, Out output, char replacement)
 {
+    static_assert(sizeof(*begin) == 2, "Character type must be 2 bytes wide");
+
     // Latin-1 is directly compatible with Unicode encodings,
     // and can thus be treated as (a sub-range of) UTF-32
     while (begin != end)
@@ -493,6 +537,8 @@ Out Utf<16>::toLatin1(In begin, In end, Out output, char replacement)
 template <typename In, typename Out>
 Out Utf<16>::toUtf8(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 2, "Character type must be 2 bytes wide");
+
     while (begin != end)
     {
         char32_t codepoint = 0;
@@ -508,6 +554,8 @@ Out Utf<16>::toUtf8(In begin, In end, Out output)
 template <typename In, typename Out>
 Out Utf<16>::toUtf16(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 2, "Character type must be 2 bytes wide");
+
     return priv::copy(begin, end, output);
 }
 
@@ -516,6 +564,8 @@ Out Utf<16>::toUtf16(In begin, In end, Out output)
 template <typename In, typename Out>
 Out Utf<16>::toUtf32(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 2, "Character type must be 2 bytes wide");
+
     while (begin != end)
     {
         char32_t codepoint = 0;
@@ -531,6 +581,8 @@ Out Utf<16>::toUtf32(In begin, In end, Out output)
 template <typename In>
 In Utf<32>::decode(In begin, In /*end*/, char32_t& output, char32_t /*replacement*/)
 {
+    static_assert(sizeof(*begin) == 4, "Character type must be 4 bytes wide");
+
     output = *begin++;
     return begin;
 }
@@ -549,6 +601,8 @@ Out Utf<32>::encode(char32_t input, Out output, char32_t /*replacement*/)
 template <typename In>
 In Utf<32>::next(In begin, In /*end*/)
 {
+    static_assert(sizeof(*begin) == 4, "Character type must be 4 bytes wide");
+
     return ++begin;
 }
 
@@ -557,6 +611,8 @@ In Utf<32>::next(In begin, In /*end*/)
 template <typename In>
 std::size_t Utf<32>::count(In begin, In end)
 {
+    static_assert(sizeof(*begin) == 4, "Character type must be 4 bytes wide");
+
     return static_cast<std::size_t>(end - begin);
 }
 
@@ -565,6 +621,8 @@ std::size_t Utf<32>::count(In begin, In end)
 template <typename In, typename Out>
 Out Utf<32>::fromAnsi(In begin, In end, Out output, const std::locale& locale)
 {
+    static_assert(sizeof(*begin) == 1, "Character type must be 1 byte wide");
+
     while (begin != end)
         *output++ = decodeAnsi(*begin++, locale);
 
@@ -576,6 +634,8 @@ Out Utf<32>::fromAnsi(In begin, In end, Out output, const std::locale& locale)
 template <typename In, typename Out>
 Out Utf<32>::fromWide(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == sizeof(wchar_t), "Character type must be same size as wchar_t");
+
     while (begin != end)
         *output++ = decodeWide(*begin++);
 
@@ -587,6 +647,8 @@ Out Utf<32>::fromWide(In begin, In end, Out output)
 template <typename In, typename Out>
 Out Utf<32>::fromLatin1(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 4, "Character type must be 4 bytes wide");
+
     // Latin-1 is directly compatible with Unicode encodings,
     // and can thus be treated as (a sub-range of) UTF-32
     return priv::copy(begin, end, output);
@@ -597,6 +659,8 @@ Out Utf<32>::fromLatin1(In begin, In end, Out output)
 template <typename In, typename Out>
 Out Utf<32>::toAnsi(In begin, In end, Out output, char replacement, const std::locale& locale)
 {
+    static_assert(sizeof(*begin) == 4, "Character type must be 4 bytes wide");
+
     while (begin != end)
         output = encodeAnsi(*begin++, output, replacement, locale);
 
@@ -608,6 +672,8 @@ Out Utf<32>::toAnsi(In begin, In end, Out output, char replacement, const std::l
 template <typename In, typename Out>
 Out Utf<32>::toWide(In begin, In end, Out output, wchar_t replacement)
 {
+    static_assert(sizeof(*begin) == 4, "Character type must be 4 bytes wide");
+
     while (begin != end)
         output = encodeWide(*begin++, output, replacement);
 
@@ -619,6 +685,8 @@ Out Utf<32>::toWide(In begin, In end, Out output, wchar_t replacement)
 template <typename In, typename Out>
 Out Utf<32>::toLatin1(In begin, In end, Out output, char replacement)
 {
+    static_assert(sizeof(*begin) == 4, "Character type must be 4 bytes wide");
+
     // Latin-1 is directly compatible with Unicode encodings,
     // and can thus be treated as (a sub-range of) UTF-32
     while (begin != end)
@@ -635,6 +703,8 @@ Out Utf<32>::toLatin1(In begin, In end, Out output, char replacement)
 template <typename In, typename Out>
 Out Utf<32>::toUtf8(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 4, "Character type must be 4 bytes wide");
+
     while (begin != end)
         output = Utf<8>::encode(*begin++, output);
 
@@ -645,6 +715,8 @@ Out Utf<32>::toUtf8(In begin, In end, Out output)
 template <typename In, typename Out>
 Out Utf<32>::toUtf16(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 4, "Character type must be 4 bytes wide");
+
     while (begin != end)
         output = Utf<16>::encode(*begin++, output);
 
@@ -656,6 +728,8 @@ Out Utf<32>::toUtf16(In begin, In end, Out output)
 template <typename In, typename Out>
 Out Utf<32>::toUtf32(In begin, In end, Out output)
 {
+    static_assert(sizeof(*begin) == 4, "Character type must be 4 bytes wide");
+
     return priv::copy(begin, end, output);
 }