diff --git a/vvp/array.cc b/vvp/array.cc
index 81f0bd065..d6287a3e9 100644
--- a/vvp/array.cc
+++ b/vvp/array.cc
@@ -545,7 +545,7 @@ void __vpiArrayVthrAPV::vpi_get_value(p_vpi_value vp)
       }
 }
 
-void __vpiArray::set_word(unsigned address, unsigned part_off, vvp_vector4_t val)
+void __vpiArray::set_word(unsigned address, unsigned part_off, const vvp_vector4_t&val)
 {
       if (address >= get_size())
 	    return;
diff --git a/vvp/vpi_priv.h b/vvp/vpi_priv.h
index 44531faf7..56f5c88d9 100644
--- a/vvp/vpi_priv.h
+++ b/vvp/vpi_priv.h
@@ -605,7 +605,7 @@ struct __vpiArray : public __vpiArrayBase, public __vpiHandle {
       inline vpiHandle vpi_iterate(int code) { return vpi_array_base_iterate(code); }
       vpiHandle vpi_index(int idx);
 
-      void set_word(unsigned idx, unsigned off, vvp_vector4_t val);
+      void set_word(unsigned idx, unsigned off, const vvp_vector4_t&val);
       void set_word(unsigned idx, double val);
       void set_word(unsigned idx, const std::string&val);
       void set_word(unsigned idx, const vvp_object_t&val);