diff --git a/include/rtl/string.hxx b/include/rtl/string.hxx
index fd65e2dfa477..d9422c696059 100644
--- a/include/rtl/string.hxx
+++ b/include/rtl/string.hxx
@@ -90,6 +90,7 @@ public:
     constexpr
 #endif
     explicit OStringLiteral(char const (&literal)[N]) {
+        assertLayout();
         assert(literal[N - 1] == '\0');
         //TODO: Use C++20 constexpr std::copy_n (P0202R3):
         for (std::size_t i = 0; i != N; ++i) {
@@ -104,6 +105,7 @@ public:
     constexpr
 #endif
     explicit OStringLiteral(char8_t const (&literal)[N]) {
+        assertLayout();
         assert(literal[N - 1] == '\0');
         //TODO: Use C++20 constexpr std::copy_n (P0202R3):
         for (std::size_t i = 0; i != N; ++i) {
@@ -116,10 +118,10 @@ public:
 
     constexpr char const * getStr() const SAL_RETURNS_NONNULL { return buffer; }
 
-    // offsetof needs a complete type, so do not have these static_asserts as class template
-    // members, but postpone their instantiation to the later non-member static_assert that calls
-    // detail_assertLayout:
-    static constexpr bool detail_assertLayout() {
+private:
+    static constexpr void assertLayout() {
+        // These static_asserts verifying the layout compatibility with rtl_String cannot be class
+        // member declarations, as offsetof requires a complete type, so defer them to here:
         static_assert(offsetof(OStringLiteral, refCount) == offsetof(rtl_String, refCount));
         static_assert(
             std::is_same_v<decltype(refCount), decltype(rtl_String::refCount)>);
@@ -130,17 +132,13 @@ public:
             std::is_same_v<
                 std::remove_extent_t<decltype(buffer)>,
                 std::remove_extent_t<decltype(rtl_String::buffer)>>);
-        return true;
     }
 
-private:
     // Same layout as rtl_String (include/rtl/string.h):
     oslInterlockedCount refCount = 0x40000000; // SAL_STRING_STATIC_FLAG (sal/rtl/strimp.hxx)
     sal_Int32 length = N - 1;
     char buffer[N] = {}; //TODO: drop initialization for C++20 (P1331R2)
 };
-
-static_assert(OStringLiteral<1>::detail_assertLayout());
 #endif
 
 /* ======================================================================= */
diff --git a/include/rtl/ustring.hxx b/include/rtl/ustring.hxx
index f458ac061ea4..707bbf6e66d6 100644
--- a/include/rtl/ustring.hxx
+++ b/include/rtl/ustring.hxx
@@ -87,6 +87,7 @@ public:
     constexpr
 #endif
     OUStringLiteral(char16_t const (&literal)[N]) {
+        assertLayout();
         assert(literal[N - 1] == '\0');
         //TODO: Use C++20 constexpr std::copy_n (P0202R3):
         for (std::size_t i = 0; i != N; ++i) {
@@ -100,10 +101,10 @@ public:
 
     constexpr operator std::u16string_view() const { return {buffer, sal_uInt32(length)}; }
 
-    // offsetof needs a complete type, so do not have these static_asserts as class template
-    // members, but postpone their instantiation to the later non-member static_assert that calls
-    // detail_assertLayout:
-    static constexpr bool detail_assertLayout() {
+private:
+    static constexpr void assertLayout() {
+        // These static_asserts verifying the layout compatibility with rtl_uString cannot be class
+        // member declarations, as offsetof requires a complete type, so defer them to here:
         static_assert(offsetof(OUStringLiteral, refCount) == offsetof(rtl_uString, refCount));
         static_assert(std::is_same_v<decltype(refCount), decltype(rtl_uString::refCount)>);
         static_assert(offsetof(OUStringLiteral, length) == offsetof(rtl_uString, length));
@@ -113,18 +114,14 @@ public:
             std::is_same_v<
                 std::remove_extent_t<decltype(buffer)>,
                 std::remove_extent_t<decltype(rtl_uString::buffer)>>);
-        return true;
     }
 
-private:
     // Same layout as rtl_uString (include/rtl/ustring.h):
     oslInterlockedCount refCount = 0x40000000; // SAL_STRING_STATIC_FLAG (sal/rtl/strimp.hxx)
     sal_Int32 length = N - 1;
     sal_Unicode buffer[N] = {}; //TODO: drop initialization for C++20 (P1331R2)
 };
 
-static_assert(OUStringLiteral<1>::detail_assertLayout());
-
 #if defined RTL_STRING_UNITTEST
 namespace libreoffice_internal {
 template<std::size_t N> struct ExceptConstCharArrayDetector<OUStringLiteral<N>> {};