diff --git a/include/sta/Debug.hh b/include/sta/Debug.hh
index dfa975aa..fc042c7d 100644
--- a/include/sta/Debug.hh
+++ b/include/sta/Debug.hh
@@ -27,11 +27,6 @@ namespace sta {
 class Report;
 class Pin;
 
-// Flag that is set when any debug mode is enabled.
-// Debug macros bypass Debug::check map lookup unless some debug mode
-// is enabled.
-extern bool debug_on;
-
 typedef Map<const char *, int, CharPtrLess> DebugMap;
 
 class Debug
@@ -52,6 +47,7 @@ public:
 
 protected:
   Report *report_;
+  bool debug_on_;
   DebugMap *debug_map_;
   int stats_level_;
 
@@ -59,22 +55,13 @@ private:
   DISALLOW_COPY_AND_ASSIGN(Debug);
 };
 
-// Low overhead predicate.
-inline bool
-debugCheck(const Debug *debug,
-	   const char *what,
-	   int level)
-{
-  return debug_on && debug->check(what, level);
-}
-
 // Inlining a varargs function would eval the args, which can
 // be expensive, so use a macro.
 // Note that "##__VA_ARGS__" is a gcc extension to support zero arguments (no comma).
 // clang -Wno-gnu-zero-variadic-macro-arguments suppresses the warning.
 // c++20 has "__VA_OPT__" to deal with the zero arg case so this is temporary.
-#define debugPrint(debug, what, level, msg, ...)     \
-  if (sta::debug_on && debug->check(what, level)) {  \
+#define debugPrint(debug, what, level, msg, ...) \
+  if (debug->check(what, level)) {  \
     debug->reportLine(what, msg, ##__VA_ARGS__); \
   }
 
diff --git a/util/Debug.cc b/util/Debug.cc
index daf47bba..b5f841a2 100644
--- a/util/Debug.cc
+++ b/util/Debug.cc
@@ -24,6 +24,7 @@ bool debug_on = false;
 
 Debug::Debug(Report *report) :
   report_(report),
+  debug_on_(false),
   debug_map_(nullptr),
   stats_level_(0)
 {
@@ -48,7 +49,8 @@ bool
 Debug::check(const char *what,
 	     int level) const
 {
-  if (debug_map_) {
+  if (debug_on_
+      && debug_map_) {
     int dbg_level;
     bool exists;
     debug_map_->findKey(what, dbg_level, exists);
@@ -88,8 +90,7 @@ Debug::setLevel(const char *what,
 	debug_map_->erase(what);
 	delete [] key;
       }
-      // debugCheck map lookup bypass
-      debug_on = (debug_map_->size() != 0);
+      debug_on_ = !debug_map_->empty();
     }
   }
   else {
@@ -98,7 +99,7 @@ Debug::setLevel(const char *what,
     if (debug_map_ == nullptr)
       debug_map_ = new DebugMap;
     (*debug_map_)[what_cpy] = level;
-    debug_on = true;
+    debug_on_ = true;
   }
 }
 
diff --git a/verilog/VerilogReader.cc b/verilog/VerilogReader.cc
index 34a45cfb..d4823dd3 100644
--- a/verilog/VerilogReader.cc
+++ b/verilog/VerilogReader.cc
@@ -206,7 +206,7 @@ VerilogReader::init(const char *filename)
   if (library_ == nullptr)
     library_ = network_->makeLibrary("verilog", nullptr);
 
-  report_stmt_stats_ = debugCheck(debug_, "verilog", 1);
+  report_stmt_stats_ = debug_->check("verilog", 1);
   module_count_ = 0;
   inst_mod_count_ = 0;
   inst_lib_count_ = 0;
@@ -694,7 +694,7 @@ VerilogReader::incrLine()
 void
 VerilogReader::reportStmtCounts()
 {
-  if (debugCheck(debug_, "verilog", 1)) {
+  if (debug_->check("verilog", 1)) {
     report_->reportLine("Verilog stats");
     printClassMemory("modules", VerilogModule, module_count_);
     printClassMemory("module insts", VerilogModuleInst, inst_mod_count_);