diff --git a/src/lib/netlist/plib/pstream.h b/src/lib/netlist/plib/pstream.h
index 7afc329e817..119ff8fbe3b 100644
--- a/src/lib/netlist/plib/pstream.h
+++ b/src/lib/netlist/plib/pstream.h
@@ -317,8 +317,8 @@ public:
 		char b[4];
 		if (m_strm.read(&b[0], 1) != 1)
 			return false;
-		const unsigned l = pstring::traits_type::codelen(b);
-		for (unsigned i = 1; i < l; i++)
+		const std::size_t l = pstring::traits_type::codelen(b);
+		for (std::size_t i = 1; i < l; i++)
 			if (m_strm.read(&b[i], 1) != 1)
 				return false;
 		c = pstring::traits_type::code(b);
diff --git a/src/lib/netlist/plib/pstring.h b/src/lib/netlist/plib/pstring.h
index 7bf1dfcd6c6..7410388af41 100644
--- a/src/lib/netlist/plib/pstring.h
+++ b/src/lib/netlist/plib/pstring.h
@@ -110,7 +110,7 @@ public:
 		const_iterator &operator=(const const_iterator &rhs) noexcept = default;
 		const_iterator &operator=(const_iterator &&rhs) noexcept = default;
 
-		const_iterator& operator++() noexcept { p += traits_type::codelen(&(*p)); return *this; }
+		const_iterator& operator++() noexcept { p += static_cast<difference_type>(traits_type::codelen(&(*p))); return *this; }
 		const_iterator operator++(int) noexcept { const_iterator tmp(*this); operator++(); return tmp; }
 
 		bool operator==(const const_iterator& rhs) const noexcept { return p == rhs.p; }