diff --git a/src/emu/emumem_het.cpp b/src/emu/emumem_het.cpp
index 87f3d35dc10..571b8246eac 100644
--- a/src/emu/emumem_het.cpp
+++ b/src/emu/emumem_het.cpp
@@ -7,8 +7,12 @@
 
 template<int Width, int AddrShift, int Endian> typename emu::detail::handler_entry_size<Width>::uX handler_entry_read_tap<Width, AddrShift, Endian>::read(offs_t offset, uX mem_mask)
 {
+	this->ref();
+
 	uX data = inh::m_next->read(offset, mem_mask);
 	m_tap(offset, data, mem_mask);
+
+	this->unref();
 	return data;
 }
 
@@ -25,8 +29,12 @@ template<int Width, int AddrShift, int Endian> handler_entry_read_tap<Width, Add
 
 template<int Width, int AddrShift, int Endian> void handler_entry_write_tap<Width, AddrShift, Endian>::write(offs_t offset, uX data, uX mem_mask)
 {
+	this->ref();
+
 	m_tap(offset, data, mem_mask);
 	inh::m_next->write(offset, data, mem_mask);
+
+	this->unref();
 }
 
 template<int Width, int AddrShift, int Endian> std::string handler_entry_write_tap<Width, AddrShift, Endian>::name() const
diff --git a/src/emu/emumem_heu.cpp b/src/emu/emumem_heu.cpp
index 51a51a70d6d..7000f77dc25 100644
--- a/src/emu/emumem_heu.cpp
+++ b/src/emu/emumem_heu.cpp
@@ -62,7 +62,7 @@ template<int Width, int AddrShift, int Endian> void handler_entry_read_units<Wid
 
 template<int Width, int AddrShift, int Endian> typename emu::detail::handler_entry_size<Width>::uX handler_entry_read_units<Width, AddrShift, Endian>::read(offs_t offset, uX mem_mask)
 {
-	ref();
+	this->ref();
 
 	uX result = m_unmap;
 	for (int index = 0; index < m_subunits; index++) {
@@ -94,7 +94,7 @@ template<int Width, int AddrShift, int Endian> typename emu::detail::handler_ent
 		}
 	}
 
-	unref();
+	this->unref();
 	return result;
 }
 
@@ -177,7 +177,7 @@ template<int Width, int AddrShift, int Endian> void handler_entry_write_units<Wi
 
 template<int Width, int AddrShift, int Endian> void handler_entry_write_units<Width, AddrShift, Endian>::write(offs_t offset, uX data, uX mem_mask)
 {
-	ref();
+	this->ref();
 
 	for (int index = 0; index < m_subunits; index++) {
 		const subunit_info &si = m_subunit_infos[index];
@@ -208,7 +208,7 @@ template<int Width, int AddrShift, int Endian> void handler_entry_write_units<Wi
 		}
 	}
 
-	unref();
+	this->unref();
 }