diff --git a/doc/release-checklist.md b/doc/release-checklist.md
index 7ce28ac0a..01fb1ece7 100644
--- a/doc/release-checklist.md
+++ b/doc/release-checklist.md
@@ -1,3 +1,5 @@
+* clang-tidy check:
+  * `cmake "-DCMAKE_CXX_CLANG_TIDY=/usr/bin/clang-tidy-9;-checks=*" ..`
 * Run tools/release.sh $OLDVERSION $VERSION
   * Finalize CHANGELOG.md
   * Bumps version numbers everywhere they need bumping
diff --git a/src/lib/cpp.h b/src/lib/cpp.h
index d287fa7be..ce8d22355 100644
--- a/src/lib/cpp.h
+++ b/src/lib/cpp.h
@@ -29,21 +29,21 @@ class ncppplot {
  static bool create(ncppplot<T>* ncpp, ncplane* n, const ncplot_options* opts, T miny, T maxy){
    // if miny == maxy, they both must be equal to 0
    if(miny == maxy && miny){
-     return NULL;
+     return false;
    }
    if(opts->rangex < 0){
-     return NULL;
+     return false;
    }
    if(maxy < miny){
-     return NULL;
+     return false;
    }
    if(opts->gridtype < 0 || opts->gridtype >= sizeof(geomdata) / sizeof(*geomdata)){
-     return NULL;
+     return false;
    }
    int sdimy, sdimx;
    ncplane_dim_yx(n, &sdimy, &sdimx);
    if(sdimx <= 0){
-     return NULL;
+     return false;
    }
    int dimx = sdimx;
    ncpp->rangex = opts->rangex;
diff --git a/src/lib/plot.cpp b/src/lib/plot.cpp
index 7a296f121..de7e83260 100644
--- a/src/lib/plot.cpp
+++ b/src/lib/plot.cpp
@@ -1,69 +1,69 @@
 #include "cpp.h"
 
-typedef struct ncuplot {
+using ncuplot = struct ncuplot {
   ncppplot<uint64_t> n;
-} ncuplot;
+};
 
-typedef struct ncdplot {
+using ncdplot = struct ncdplot {
   ncppplot<double> n;
-} ncdplot;
+};
 
 extern "C" {
 
-ncuplot* ncuplot_create(ncplane* n, const ncplot_options* opts, uint64_t miny, uint64_t maxy){
+ncuplot* ncuplot_create(ncplane* n, const ncplot_options* opts, uint64_t miny, uint64_t maxy) {
   auto ret = new ncuplot;
   if(ret){
     if(ncppplot<uint64_t>::create(&ret->n, n, opts, miny, maxy)){
       return ret;
     }
-    free(ret);
+    delete ret;
   }
   return nullptr;
 }
 
-ncplane* ncuplot_plane(ncuplot* n){
+ncplane* ncuplot_plane(ncuplot* n) {
   return n->n.ncp;
 }
 
-int ncuplot_add_sample(ncuplot* n, uint64_t x, uint64_t y){
+int ncuplot_add_sample(ncuplot* n, uint64_t x, uint64_t y) {
   return n->n.add_sample(x, y);
 }
 
-int ncuplot_set_sample(ncuplot* n, uint64_t x, uint64_t y){
+int ncuplot_set_sample(ncuplot* n, uint64_t x, uint64_t y) {
   return n->n.set_sample(x, y);
 }
 
-void ncuplot_destroy(ncuplot* n){
+void ncuplot_destroy(ncuplot* n) {
   if(n){
     n->n.destroy();
     delete n;
   }
 }
 
-ncdplot* ncdplot_create(ncplane* n, const ncplot_options* opts, double miny, double maxy){
+ncdplot* ncdplot_create(ncplane* n, const ncplot_options* opts, double miny, double maxy) {
   auto ret = new ncdplot;
   if(ret){
     if(ncppplot<double>::create(&ret->n, n, opts, miny, maxy)){
       return ret;
     }
-    free(ret);
+    delete ret;
   }
   return nullptr;
 }
 
-ncplane* ncdplot_plane(ncdplot* n){
+ncplane* ncdplot_plane(ncdplot* n) {
   return n->n.ncp;
 }
 
-int ncdplot_add_sample(ncdplot* n, uint64_t x, double y){
+int ncdplot_add_sample(ncdplot* n, uint64_t x, double y) {
   return n->n.add_sample(x, y);
 }
 
-int ncdplot_set_sample(ncdplot* n, uint64_t x, double y){
+int ncdplot_set_sample(ncdplot* n, uint64_t x, double y) {
   return n->n.set_sample(x, y);
 }
 
-void ncdplot_destroy(ncdplot* n){
+void ncdplot_destroy(ncdplot* n) {
   if(n){
     n->n.destroy();
     delete n;
diff --git a/tests/zaxis.cpp b/tests/zaxis.cpp
index a4fafd7cc..4f72cf3f0 100644
--- a/tests/zaxis.cpp
+++ b/tests/zaxis.cpp
@@ -9,7 +9,7 @@ TEST_CASE("ZAxisTest") {
   notcurses_options nopts{};
   nopts.inhibit_alternate_screen = true;
   nopts.suppress_banner = true;
-  FILE* outfp_ = fopen("/dev/tty", "wb");
+  FILE* outfp_ = fopen("/dev/tty", "wbe");
   REQUIRE(outfp_);
   struct notcurses* nc_ = notcurses_init(&nopts, outfp_);
   REQUIRE(nc_);