diff --git a/NEWS.md b/NEWS.md
index 61e1ca659..be330de2f 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -5,6 +5,9 @@ rearrangements of Notcurses.
   * `ncplane_qrcode()` no longer accepts a blitter argument, since `NCBLIT_2x1`
     is the only one that actually works with qr code scanners. I'm unaware of
     any external `ncplane_qrcode()` users, so hopefully this isn't a problem.
+  * `notcurses_stats()` no longer qualifies its `notcurses*` argument with
+    `const`, since it now takes a lock. I'm sorry about that, though on the
+    plus side, data races can no longer result in invalid stats.
 
 * 2.2.1 (2021-02-09):
   * Brown-bag release: fix UTF8 discovery in direct mode. Sorry!
diff --git a/USAGE.md b/USAGE.md
index fe917035c..0340b0417 100644
--- a/USAGE.md
+++ b/USAGE.md
@@ -3062,13 +3062,13 @@ typedef struct ncstats {
 ncstats* notcurses_stats_alloc(const struct notcurses* nc);
 
 // Acquire an atomic snapshot of the Notcurses object's stats.
-void notcurses_stats(const struct notcurses* nc, ncstats* stats);
+void notcurses_stats(struct notcurses* nc, ncstats* stats);
 
-// Reset all cumulative stats (immediate ones, such as fbbytes, are not reset).
+// Reset all cumulative stats (immediate ones, such as fbbytes, are not reset),
+// first copying them into |*stats| (if |stats| is not NULL).
 void notcurses_stats_reset(struct notcurses* nc, ncstats* stats);
 ```
 
-
 ## C++
 
 Marek Habersack has contributed (and maintains) C++ wrappers installed to
diff --git a/include/notcurses/notcurses.h b/include/notcurses/notcurses.h
index 41821e404..757af9ffe 100644
--- a/include/notcurses/notcurses.h
+++ b/include/notcurses/notcurses.h
@@ -1276,13 +1276,17 @@ typedef struct ncstats {
 
 // Allocate an ncstats object. Use this rather than allocating your own, since
 // future versions of Notcurses might enlarge this structure.
-API ALLOC ncstats* notcurses_stats_alloc(const struct notcurses* nc);
+API ALLOC ncstats* notcurses_stats_alloc(const struct notcurses* nc)
+  __attribute__ ((nonnull(1)));
 
 // Acquire an atomic snapshot of the Notcurses object's stats.
-API void notcurses_stats(const struct notcurses* nc, ncstats* stats);
+API void notcurses_stats(struct notcurses* nc, ncstats* stats)
+  __attribute__ ((nonnull(1, 2)));
 
-// Reset all cumulative stats (immediate ones, such as fbbytes, are not reset).
-API void notcurses_stats_reset(struct notcurses* nc, ncstats* stats);
+// Reset all cumulative stats (immediate ones, such as fbbytes, are not reset),
+// first copying them into |*stats| (if |stats| is not NULL).
+API void notcurses_stats_reset(struct notcurses* nc, ncstats* stats)
+  __attribute__ ((nonnull(1)));
 
 // Resize the specified ncplane. The four parameters 'keepy', 'keepx',
 // 'keepleny', and 'keeplenx' define a subset of the ncplane to keep,
diff --git a/src/lib/internal.h b/src/lib/internal.h
index 2257a2f5e..492a0024a 100644
--- a/src/lib/internal.h
+++ b/src/lib/internal.h
@@ -348,6 +348,7 @@ typedef struct notcurses {
   int cursory;    // desired cursor placement according to user.
   int cursorx;    // -1 is don't-care, otherwise moved here after each render.
 
+  pthread_mutex_t statlock;
   ncstats stats;  // some statistics across the lifetime of the notcurses ctx
 
   FILE* ttyfp;    // FILE* for writing rasterized data
diff --git a/src/lib/notcurses.c b/src/lib/notcurses.c
index c822c6a80..9d19194cb 100644
--- a/src/lib/notcurses.c
+++ b/src/lib/notcurses.c
@@ -221,10 +221,12 @@ void free_plane(ncplane* p){
   if(p){
     // ncdirect fakes an ncplane with no ->pile
     if(ncplane_pile(p)){
+      notcurses* nc = ncplane_notcurses(p);
+      pthread_mutex_lock(&nc->statlock);
       --ncplane_notcurses(p)->stats.planes;
       ncplane_notcurses(p)->stats.fbbytes -= sizeof(*p->fb) * p->leny * p->lenx;
+      pthread_mutex_unlock(&nc->statlock);
       if(p->above == NULL && p->below == NULL){
-        struct notcurses* nc = ncplane_notcurses(p);
         pthread_mutex_lock(&nc->pilelock);
         ncpile_destroy(ncplane_pile(p));
         pthread_mutex_unlock(&nc->pilelock);
@@ -357,8 +359,10 @@ ncplane* ncplane_new_internal(notcurses* nc, ncplane* n,
     }else{ // new pile
       make_ncpile(nc, p);
     }
+    pthread_mutex_lock(&nc->statlock);
     nc->stats.fbbytes += fbsize;
     ++nc->stats.planes;
+    pthread_mutex_unlock(&nc->statlock);
     pthread_mutex_unlock(&nc->pilelock);
   }
   loginfo(nc, "Created new %dx%d plane \"%s\" @ %dx%d\n",
@@ -541,6 +545,7 @@ int ncplane_resize_internal(ncplane* n, int keepy, int keepx, int keepleny,
     return -1;
   }
   loginfo(ncplane_notcurses(n), "%dx%d @ %d/%d → %d/%d @ %d/%d (keeping %dx%d from %d/%d)\n", rows, cols, n->absy, n->absx, ylen, xlen, n->absy + keepy + yoff, n->absx + keepx + xoff, keepleny, keeplenx, keepy, keepx);
+  notcurses* nc = ncplane_notcurses(n);
   // we're good to resize. we'll need alloc up a new framebuffer, and copy in
   // those elements we're retaining, zeroing out the rest. alternatively, if
   // we've shrunk, we will be filling the new structure.
@@ -559,8 +564,10 @@ int ncplane_resize_internal(ncplane* n, int keepy, int keepx, int keepleny,
     n->x = xlen - 1;
   }
   nccell* preserved = n->fb;
+  pthread_mutex_lock(&nc->statlock);
   ncplane_notcurses(n)->stats.fbbytes -= sizeof(*preserved) * (rows * cols);
   ncplane_notcurses(n)->stats.fbbytes += fbsize;
+  pthread_mutex_unlock(&nc->statlock);
   n->fb = fb;
   const int oldabsy = n->absy;
   // go ahead and move. we can no longer fail at this point. but don't yet
@@ -712,8 +719,10 @@ reset_stats(ncstats* stats){
   stats->planes = planes;
 }
 
-void notcurses_stats(const notcurses* nc, ncstats* stats){
+void notcurses_stats(notcurses* nc, ncstats* stats){
+  pthread_mutex_lock(&nc->statlock);
   memcpy(stats, &nc->stats, sizeof(*stats));
+  pthread_mutex_unlock(&nc->statlock);
 }
 
 ncstats* notcurses_stats_alloc(const notcurses* nc __attribute__ ((unused))){
@@ -721,10 +730,12 @@ ncstats* notcurses_stats_alloc(const notcurses* nc __attribute__ ((unused))){
 }
 
 void notcurses_stats_reset(notcurses* nc, ncstats* stats){
+  pthread_mutex_lock(&nc->statlock);
   if(stats){
     memcpy(stats, &nc->stats, sizeof(*stats));
   }
   reset_stats(&nc->stats);
+  pthread_mutex_unlock(&nc->statlock);
 }
 
 // unless the suppress_banner flag was set, print some version information and
@@ -879,6 +890,7 @@ recursive_lock_init(pthread_mutex_t *lock){
 #endif
 }
 
+// FIXME cut this up into a few distinct pieces, yearrrgh
 notcurses* notcurses_core_init(const notcurses_options* opts, FILE* outfp){
   notcurses_options defaultopts;
   memset(&defaultopts, 0, sizeof(defaultopts));
@@ -915,11 +927,6 @@ notcurses* notcurses_core_init(const notcurses_options* opts, FILE* outfp){
   if(outfp == NULL){
     outfp = stdout;
   }
-  if(recursive_lock_init(&ret->pilelock)){
-    fprintf(stderr, "Couldn't initialize pile mutex\n");
-    free(ret);
-    return NULL;
-  }
   ret->margin_t = opts->margin_t;
   ret->margin_b = opts->margin_b;
   ret->margin_l = opts->margin_l;
@@ -956,6 +963,16 @@ notcurses* notcurses_core_init(const notcurses_options* opts, FILE* outfp){
   }else{
     fprintf(stderr, "Defaulting to %dx%d (output is not to a terminal)\n", DEFAULT_ROWS, DEFAULT_COLS);
   }
+  if(recursive_lock_init(&ret->pilelock)){
+    fprintf(stderr, "Couldn't initialize pile mutex\n");
+    free(ret);
+    return NULL;
+  }
+  if(pthread_mutex_init(&ret->statlock, NULL)){
+    pthread_mutex_destroy(&ret->pilelock);
+    free(ret);
+    return NULL;
+  }
   if(setup_signals(ret, (opts->flags & NCOPTION_NO_QUIT_SIGHANDLERS),
                    (opts->flags & NCOPTION_NO_WINCH_SIGHANDLER),
                    notcurses_stop_minimal)){
@@ -1046,6 +1063,8 @@ err:
   // FIXME looks like we have some memory leaks on this error path?
   tcsetattr(ret->ttyfd, TCSANOW, &ret->tpreserved);
   drop_signals(ret);
+  pthread_mutex_destroy(&ret->statlock);
+  pthread_mutex_destroy(&ret->pilelock);
   free(ret);
   return NULL;
 }
@@ -1172,6 +1191,7 @@ int notcurses_stop(notcurses* nc){
       }
     }
     del_curterm(cur_term);
+    ret |= pthread_mutex_destroy(&nc->statlock);
     ret |= pthread_mutex_destroy(&nc->pilelock);
     free(nc);
   }
diff --git a/src/lib/render.c b/src/lib/render.c
index 75d26adad..d8bf9faf0 100644
--- a/src/lib/render.c
+++ b/src/lib/render.c
@@ -97,7 +97,7 @@ blocking_write(int fd, const char* buf, size_t buflen){
   return 0;
 }
 
-// update timings for writeout. only call on success.
+// update timings for writeout. only call on success. call only under statlock.
 static void
 update_write_stats(const struct timespec* time1, const struct timespec* time0,
                    ncstats* stats, int bytes){
@@ -118,7 +118,7 @@ update_write_stats(const struct timespec* time1, const struct timespec* time0,
   }
 }
 
-// negative 'bytes' is recorded as a failure.
+// negative 'bytes' is recorded as a failure. call only while holding statlock.
 static void
 update_render_bytes(ncstats* stats, int bytes){
   if(bytes >= 0){
@@ -134,6 +134,7 @@ update_render_bytes(ncstats* stats, int bytes){
   }
 }
 
+// call only while holding statlock.
 static void
 update_render_stats(const struct timespec* time1, const struct timespec* time0,
                     ncstats* stats){
@@ -152,6 +153,7 @@ update_render_stats(const struct timespec* time1, const struct timespec* time0,
   }
 }
 
+// call only while holding statlock.
 static void
 update_raster_stats(const struct timespec* time1, const struct timespec* time0,
                     ncstats* stats){
@@ -1200,10 +1202,12 @@ int ncpile_rasterize(ncplane* n){
   clock_gettime(CLOCK_MONOTONIC, &rasterdone);
   int bytes = notcurses_rasterize(nc, pile, nc->rstate.mstreamfp);
   // accepts -1 as an indication of failure
-  update_render_bytes(&nc->stats, bytes);
   clock_gettime(CLOCK_MONOTONIC, &writedone);
+  pthread_mutex_lock(&nc->statlock);
+  update_render_bytes(&nc->stats, bytes);
   update_raster_stats(&rasterdone, &start, &nc->stats);
   update_write_stats(&writedone, &rasterdone, &nc->stats, bytes);
+  pthread_mutex_unlock(&nc->statlock);
   if(bytes < 0){
     return -1;
   }
@@ -1246,7 +1250,9 @@ int ncpile_render(ncplane* n){
                          notcurses_stdplane(nc)->absy,
                          notcurses_stdplane(nc)->absx);
   clock_gettime(CLOCK_MONOTONIC, &renderdone);
+  pthread_mutex_lock(&nc->statlock);
   update_render_stats(&renderdone, &start, &nc->stats);
+  pthread_mutex_unlock(&nc->statlock);
   return 0;
 }
 
@@ -1267,7 +1273,9 @@ int notcurses_render_to_buffer(notcurses* nc, char** buf, size_t* buflen){
     return -1;
   }
   int bytes = notcurses_rasterize_inner(nc, ncplane_pile(stdn), nc->rstate.mstreamfp);
+  pthread_mutex_lock(&nc->statlock);
   update_render_bytes(&nc->stats, bytes);
+  pthread_mutex_unlock(&nc->statlock);
   if(bytes < 0){
     return -1;
   }