diff --git a/.clang-tidy b/.clang-tidy
index c095fa1b..6d1a84c2 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -76,5 +76,7 @@ HeaderFilterRegex: '.*/(app|cmake|dcalc|graph|liberty|network|parasitics|power|s
 # util/gzstream.hh
 # util/FlexDisableRegister.hh
 # Bison-generated parser headers (build/{Liberty,Verilog,...}Parse.hh)
-ExcludeHeaderFilterRegex: '(.*/)?(gzstream\.hh|FlexDisableRegister\.hh|(Liberty|Verilog|Sdf|Spef|Saif|LibExpr)Parse\.hh)$'
+# Homebrew and MacPorts third-party headers.
+ExcludeHeaderFilterRegex: '(^/opt/(homebrew|local)/.*)|((.*/)?(gzstream\.hh|FlexDisableRegister\.hh|(Liberty|Verilog|Sdf|Spef|Saif|LibExpr)Parse\.hh)$)'
+SystemHeaders: false
 FormatStyle: none
diff --git a/dcalc/Arnoldi.hh b/dcalc/Arnoldi.hh
index ccfbb002..ac577565 100644
--- a/dcalc/Arnoldi.hh
+++ b/dcalc/Arnoldi.hh
@@ -69,7 +69,6 @@ class rcmodel : public ConcreteParasitic,
                 public arnoldi1
 {
 public:
-  rcmodel();
   ~rcmodel() override;
   float capacitance() const override;
   PinSet unannotatedLoads(const Pin *drvr_pin,
diff --git a/dcalc/ArnoldiReduce.cc b/dcalc/ArnoldiReduce.cc
index 236c01a6..c9940ae4 100644
--- a/dcalc/ArnoldiReduce.cc
+++ b/dcalc/ArnoldiReduce.cc
@@ -43,12 +43,11 @@ namespace sta {
 // This is legacy C-style code.
 // NOLINTBEGIN(modernize-avoid-c-style-cast, bugprone-multi-level-implicit-pointer-conversion, bugprone-implicit-widening-of-multiplication-result)
 
-rcmodel::rcmodel()
+rcmodel::~rcmodel()
 {
+  free(pinV);
 }
 
-rcmodel::~rcmodel() { free(pinV); }
-
 float
 rcmodel::capacitance() const
 {