diff --git a/vvp/config.h.in b/vvp/config.h.in
index fe7e0d3b5..0a41bd44f 100644
--- a/vvp/config.h.in
+++ b/vvp/config.h.in
@@ -65,14 +65,13 @@
 # include  <inttypes.h>
 #endif
 
-# define UL_AND_TIME64_DIFF 1
 #if SIZEOF_UNSIGNED >= 8
 typedef unsigned vvp_time64_t;
 # define TIME_FMT ""
 #else
 # if SIZEOF_UNSIGNED_LONG >= 8
 typedef unsigned long vvp_time64_t;
-#  define UL_AND_TIME64_DIFF 0
+#  define UL_AND_TIME64_SAME
 #  define TIME_FMT "l"
 # else
 #  if SIZEOF_UNSIGNED_LONG_LONG > SIZEOF_UNSIGNED_LONG
@@ -80,7 +79,7 @@ typedef unsigned long long vvp_time64_t;
 #   define TIME_FMT "ll"
 #  else
 typedef unsigned long vvp_time64_t;
-#   define UL_AND_TIME64_DIFF 0
+#   define UL_AND_TIME64_SAME
 #   define TIME_FMT "l"
 #  endif
 # endif
diff --git a/vvp/vvp_net.cc b/vvp/vvp_net.cc
index 18dc3bd8f..1a8ab4c86 100644
--- a/vvp/vvp_net.cc
+++ b/vvp/vvp_net.cc
@@ -1209,7 +1209,7 @@ bool vector4_to_value(const vvp_vector4_t&vec, unsigned long&val)
       return true;
 }
 
-#if UL_AND_TIME64_DIFF
+#ifndef UL_AND_TIME64_SAME
 bool vector4_to_value(const vvp_vector4_t&vec, vvp_time64_t&val)
 {
       vvp_time64_t res = 0;
diff --git a/vvp/vvp_net.h b/vvp/vvp_net.h
index 622af0d4c..97070e65e 100644
--- a/vvp/vvp_net.h
+++ b/vvp/vvp_net.h
@@ -394,7 +394,7 @@ template <class T> extern T coerce_to_width(const T&that, unsigned width);
  */
 extern bool vector4_to_value(const vvp_vector4_t&a, long&val, bool is_signed, bool is_arithmetic =true);
 extern bool vector4_to_value(const vvp_vector4_t&a, unsigned long&val);
-#if UL_AND_TIME64_DIFF
+#ifndef UL_AND_TIME64_SAME
 extern bool vector4_to_value(const vvp_vector4_t&a, vvp_time64_t&val);
 #endif
 extern bool vector4_to_value(const vvp_vector4_t&a, double&val, bool is_signed);