diff --git a/ucb/source/ucp/file/filglob.cxx b/ucb/source/ucp/file/filglob.cxx
index ce719986961f..93fb4ad81a4d 100644
--- a/ucb/source/ucp/file/filglob.cxx
+++ b/ucb/source/ucp/file/filglob.cxx
@@ -187,7 +187,7 @@ namespace fileaccess {
     std::u16string_view getTitle( std::u16string_view aPath )
     {
         size_t lastIndex = aPath.rfind( '/' );
-        return aPath.substr( lastIndex + 1 );
+        return aPath.substr((lastIndex != std::u16string_view::npos) ? lastIndex + 1 : 0);
     }
 
 
diff --git a/unodevtools/source/skeletonmaker/javatypemaker.cxx b/unodevtools/source/skeletonmaker/javatypemaker.cxx
index 639438799d48..49a86e87d866 100644
--- a/unodevtools/source/skeletonmaker/javatypemaker.cxx
+++ b/unodevtools/source/skeletonmaker/javatypemaker.cxx
@@ -252,7 +252,8 @@ static void printConstructor(
     rtl::Reference< unoidl::Entity > const & entity, std::u16string_view name,
     std::vector< OUString > const & arguments)
 {
-    o << "public " << OUString(name.substr(name.rfind('.') + 1)) << '(';
+    std::u16string_view::size_type pos = name.rfind('.');
+    o << "public " << OUString(name.substr((pos != std::u16string_view::npos) ? pos + 1 : 0)) << '(';
     printConstructorParameters(
         o, options, manager, sort, entity, name, arguments);
     o << ");\n";
diff --git a/unoidl/source/sourceprovider-parser.y b/unoidl/source/sourceprovider-parser.y
index 0ce80ac5d9ac..2b126d4811bb 100644
--- a/unoidl/source/sourceprovider-parser.y
+++ b/unoidl/source/sourceprovider-parser.y
@@ -168,7 +168,8 @@ template<typename T> rtl::Reference<T> getCurrentPad(
 
 bool nameHasSameIdentifierAs(std::u16string_view name, std::u16string_view identifier)
 {
-    size_t i = name.rfind('.') + 1;
+    std::u16string_view::size_type pos = name.rfind('.');
+    size_t i = (pos != std::u16string_view::npos) ? pos + 1 : 0;
     return identifier.size() == name.size() - i
         && o3tl::starts_with(name.substr(i), identifier);
 }