diff --git a/configure.in b/configure.in
index 4248e7fad..83e0fe50e 100644
--- a/configure.in
+++ b/configure.in
@@ -135,6 +135,7 @@ CXXFLAGS="$iverilog_temp_cxxflags"
 AC_CHECK_SIZEOF(unsigned long long)
 AC_CHECK_SIZEOF(unsigned long)
 AC_CHECK_SIZEOF(unsigned)
+AC_CHECK_SIZEOF(void *)
 
 # vvp uses these...
 AC_CHECK_LIB(termcap, tputs)
diff --git a/vvp/config.h.in b/vvp/config.h.in
index 20f56925b..ee5862707 100644
--- a/vvp/config.h.in
+++ b/vvp/config.h.in
@@ -32,6 +32,7 @@
 # define SIZEOF_UNSIGNED_LONG 0
 #endif
 # define SIZEOF_UNSIGNED 0
+# define SIZEOF_VOID_P 0
 
 # undef NEED_LU
 # undef NEED_TU
@@ -127,6 +128,16 @@ typedef unsigned long vvp_time64_t;
 
 #endif /* HAVE_INTTYPES_H */
 
+# if SIZEOF_VOID_P == SIZEOF_UNSIGNED_LONG
+#  define UINTPTR_C(n) n ## UL
+# else
+#  if SIZEOF_VOID_P == SIZEOF_UNSIGNED_LONG_LONG
+#   define UINTPTR_C(n) n ## ULL
+#  else
+#   error "Unexpected pointer size"
+#  endif
+# endif
+
 # include  <cmath>
 
 /* getrusage, /proc/self/statm */
diff --git a/vvp/vvp_net.h b/vvp/vvp_net.h
index b1ffd3cc7..75c7b3d2a 100644
--- a/vvp/vvp_net.h
+++ b/vvp/vvp_net.h
@@ -1050,20 +1050,20 @@ template <class T> class vvp_sub_pointer_t {
       vvp_sub_pointer_t(T*ptr__, unsigned port__)
       {
 	    bits_ = reinterpret_cast<uintptr_t> (ptr__);
-	    assert( (bits_  &  3) == 0 );
-	    assert( (port__ & ~3) == 0 );
+	    assert( (bits_  &  UINTPTR_C(3)) == 0 );
+	    assert( (port__ & ~UINTPTR_C(3)) == 0 );
 	    bits_ |= port__;
       }
 
       ~vvp_sub_pointer_t() { }
 
       T* ptr()
-      { return reinterpret_cast<T*> (bits_ & ~3UL); }
+      { return reinterpret_cast<T*> (bits_ & ~UINTPTR_C(3)); }
 
       const T* ptr() const
-      { return reinterpret_cast<const T*> (bits_ & ~3UL); }
+      { return reinterpret_cast<const T*> (bits_ & ~UINTPTR_C(3)); }
 
-      unsigned  port() const { return bits_ & 3; }
+      unsigned  port() const { return bits_ & UINTPTR_C(3); }
 
       bool nil() const { return bits_ == 0; }