diff --git a/include/sta/Units.hh b/include/sta/Units.hh
index c9e5baa6..541a8162 100644
--- a/include/sta/Units.hh
+++ b/include/sta/Units.hh
@@ -16,13 +16,16 @@
 
 #pragma once
 
+#include <string>
+
 namespace sta {
 
+using std::string;
+
 class Unit
 {
 public:
   Unit(const char *suffix);
-  ~Unit();
   Unit(float scale,
        const char *suffix,
        int digits);
@@ -34,9 +37,9 @@ public:
   float scale() const { return scale_; }
   void setScale(float scale);
   const char *scaleAbbreviation() const;
-  const char *suffix() const { return suffix_; }
+  const char *suffix() const { return suffix_.c_str(); }
   // scale abbreviation + suffix
-  const char *scaledSuffix() const { return scaled_suffix_; }
+  const char *scaledSuffix() const { return scaled_suffix_.c_str(); }
   void setSuffix(const char *suffix);
   int digits() const { return digits_; }
   void setDigits(int digits);
@@ -51,8 +54,8 @@ private:
   void setScaledSuffix();
 
   float scale_;			// multiplier from user units to internal units
-  const char *suffix_;		// print suffix
-  const char *scaled_suffix_;
+  string suffix_;		// print suffix
+  string scaled_suffix_;
   int digits_;			// print digits (after decimal pt)
 };
 
diff --git a/liberty/Units.cc b/liberty/Units.cc
index 9b24173c..4874c19b 100644
--- a/liberty/Units.cc
+++ b/liberty/Units.cc
@@ -29,8 +29,7 @@ using std::abs;
 
 Unit::Unit(const char *suffix) :
   scale_(1.0),
-  suffix_(stringCopy(suffix)),
-  scaled_suffix_(nullptr),
+  suffix_(suffix),
   digits_(3)
 {
   setScaledSuffix();
@@ -40,8 +39,7 @@ Unit::Unit(float scale,
 	   const char *suffix,
 	   int digits) :
   scale_(scale),
-  suffix_(stringCopy(suffix)),
-  scaled_suffix_(nullptr),
+  suffix_(suffix),
   digits_(digits)
 {
   setScaledSuffix();
@@ -50,24 +48,15 @@ Unit::Unit(float scale,
 void
 Unit::setScaledSuffix()
 {
-  stringDelete(scaled_suffix_);
-  scaled_suffix_ = stringPrint("%s%s", scaleAbbreviation(), suffix_);
-}
-
-Unit::~Unit()
-{
-  stringDelete(suffix_);
-  stringDelete(scaled_suffix_);
+  scaled_suffix_ = scaleAbbreviation() + suffix_;
 }
 
 void
 Unit::operator=(const Unit &unit)
 {
   scale_ = unit.scale_;
-  stringDelete(suffix_);
-  suffix_ = stringCopy(unit.suffix_);
-  stringDelete(scaled_suffix_);
-  scaled_suffix_ = stringCopy(unit.scaled_suffix_);
+  suffix_ = unit.suffix_;
+  scaled_suffix_ = unit.scaled_suffix_;
   digits_ = unit.digits_;
 }
 
@@ -116,8 +105,7 @@ Unit::scaleAbbreviation() const
 void
 Unit::setSuffix(const char *suffix)
 {
-  stringDelete(suffix_);
-  suffix_ = stringCopy(suffix);
+  suffix_ = suffix;
   setScaledSuffix();
 }