diff --git a/src/rba/rba/rba.cc b/src/rba/rba/rba.cc
index ec6cb898f..8ebf6c12f 100644
--- a/src/rba/rba/rba.cc
+++ b/src/rba/rba/rba.cc
@@ -1448,7 +1448,7 @@ rba_add_path (const std::string &path)
 {
   VALUE pv = rb_gv_get ("$:");
   if (pv != Qnil && TYPE (pv) == T_ARRAY) {
-    rb_ary_push (pv, rb_str_new (path.c_str (), path.size ()));
+    rb_ary_push (pv, rb_str_new (path.c_str (), long (path.size ())));
   }
 }
 
@@ -1953,7 +1953,7 @@ RubyInterpreter::load_file (const std::string &filename_utf8)
 {
   std::string fl (rb_cstring_from_utf8 (filename_utf8));
 
-  rb_set_progname (rb_str_new (fl.c_str (), fl.size ()));
+  rb_set_progname (rb_str_new (fl.c_str (), long (fl.size ())));
 
   rb_set_errinfo (Qnil);
   int error = 0;
@@ -1961,7 +1961,7 @@ RubyInterpreter::load_file (const std::string &filename_utf8)
   rb_protect_init (); // see above
 
   RUBY_BEGIN_EXEC
-    rb_load_protect (rb_str_new (fl.c_str (), fl.size ()), wrap, &error);
+    rb_load_protect (rb_str_new (fl.c_str (), long (fl.size ())), wrap, &error);
   RUBY_END_EXEC
 
   if (error) {
@@ -2003,7 +2003,7 @@ RubyInterpreter::eval_string_and_print (const char *expr, const char *file, int
 void
 RubyInterpreter::define_variable (const std::string &name, const std::string &value)
 {
-  rb_gv_set (name.c_str (), rb_str_new (value.c_str (), value.size ()));
+  rb_gv_set (name.c_str (), rb_str_new (value.c_str (), long (value.size ())));
 }
 
 gsi::Inspector *
diff --git a/src/rba/rba/rbaConvert.h b/src/rba/rba/rbaConvert.h
index 5f0d8c344..c334d6dc3 100644
--- a/src/rba/rba/rbaConvert.h
+++ b/src/rba/rba/rbaConvert.h
@@ -447,7 +447,7 @@ inline VALUE c2ruby<float> (const float &c)
 template <>
 inline VALUE c2ruby<std::string> (const std::string &c)
 {
-  return rb_str_new (c.c_str (), c.size ());
+  return rb_str_new (c.c_str (), long (c.size ()));
 }
 
 #if defined(HAVE_QT)
@@ -468,7 +468,7 @@ inline VALUE c2ruby<QString> (const QString &qs)
     return Qnil;
   } else {
     std::string c (tl::to_string (qs));
-    return rb_str_new (c.c_str (), c.size ());
+    return rb_str_new (c.c_str (), long (c.size ()));
   }
 }
 #endif
@@ -489,7 +489,7 @@ inline VALUE c2ruby<const char *> (const char * const & s)
     static const char null_string[] = "(null)";
     return rb_str_new (null_string, sizeof (null_string) - 1);
   } else {
-    return rb_str_new (s, strlen (s));
+    return rb_str_new (s, long (strlen (s)));
   }
 }
 
diff --git a/src/rba/rba/rbaInternal.cc b/src/rba/rba/rbaInternal.cc
index 4c134e0cf..d6d8dc302 100644
--- a/src/rba/rba/rbaInternal.cc
+++ b/src/rba/rba/rbaInternal.cc
@@ -495,7 +495,7 @@ Proxy::initialize_callbacks ()
       //  There is no place in the ruby API to determine whether a method is defined.
       //  Instead we explicitly call "method_defined?" to check, whether the given method
       //  is defined.
-      VALUE name = rb_str_new (nstr, strlen (nstr));
+      VALUE name = rb_str_new (nstr, long (strlen (nstr)));
       RB_GC_GUARD (name);
 
       for (int prot = 0; prot < 2; ++prot) {
diff --git a/src/rba/rba/rbaMarshal.cc b/src/rba/rba/rbaMarshal.cc
index dbfe9ddc8..3af484f31 100644
--- a/src/rba/rba/rbaMarshal.cc
+++ b/src/rba/rba/rbaMarshal.cc
@@ -538,7 +538,7 @@ struct reader<gsi::StringType>
     if (!a.get ()) {
       *ret = Qnil;
     } else {
-      *ret = rb_str_new (a->c_str (), a->size ());
+      *ret = rb_str_new (a->c_str (), long (a->size ()));
     }
   }
 };
@@ -720,7 +720,7 @@ RubyBasedVectorAdaptorIterator::RubyBasedVectorAdaptorIterator (VALUE array, con
 
 void RubyBasedVectorAdaptorIterator::get (gsi::SerialArgs &w, tl::Heap &heap) const
 {
-  gsi::do_on_type<writer> () (mp_ainner->type (), &w, rb_ary_entry (m_array, m_i), *mp_ainner, &heap);
+  gsi::do_on_type<writer> () (mp_ainner->type (), &w, rb_ary_entry (m_array, long (m_i)), *mp_ainner, &heap);
 }
 
 bool RubyBasedVectorAdaptorIterator::at_end () const
diff --git a/src/rba/rba/rbaUtils.cc b/src/rba/rba/rbaUtils.cc
index 1cb6ca63b..7d8704acf 100644
--- a/src/rba/rba/rbaUtils.cc
+++ b/src/rba/rba/rbaUtils.cc
@@ -505,15 +505,15 @@ VALUE rba_eval_string_in_context (const char *expr, const char *file, int line,
   rb_set_errinfo (Qnil);
 
   if (file) {
-    rb_set_progname (rb_str_new (file, strlen (file)));
+    rb_set_progname (rb_str_new (file, long (strlen (file))));
   } else {
     const char *e = "<immediate>";
-    rb_set_progname (rb_str_new (e, strlen (e)));
+    rb_set_progname (rb_str_new (e, long (strlen (e))));
   }
 
   int argc;
   VALUE args[4];
-  args[0] = rb_str_new (expr, strlen (expr));
+  args[0] = rb_str_new (expr, long (strlen (expr)));
   //  use the current binding if there is one. This allows to eval in the context of a current trace callback
   //  when eval is called from the trace handler.
   if (context < 0) {
@@ -529,7 +529,7 @@ VALUE rba_eval_string_in_context (const char *expr, const char *file, int line,
     args[1] = rb_binding_new ();
   }
   if (file) {
-    args[2] = rb_str_new (file, strlen (file));
+    args[2] = rb_str_new (file, long (strlen (file)));
     args[3] = INT2NUM(line);
     argc = 4;
   } else {