diff --git a/mongoose.c b/mongoose.c
index 23551cca..86a302e4 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -3913,29 +3913,28 @@ size_t mg_usage(int task, int metric) {
 }
 #endif
 
-static size_t print_stacks(mg_pfn_t fn, void *arg, va_list *ap) {
-  int i;
-  int count = (int) mg_usage(-1, MG_USAGE_NUM_TASKS);
-  size_t len = mg_xprintf(fn, arg, "[");
-  for (i = 0; i < count; i++) {
-    const char *name = (const char *) mg_usage(i, MG_USAGE_TASK_NAME);
-    len += mg_xprintf(fn, arg, "%s{%m:%m,%m:%zu,%m:%zu}",
-                      i == 0 ? "" : ",", MG_ESC("name"),
-                      MG_ESC(name == NULL ? "" : name), MG_ESC("free"),
-                      (size_t) mg_usage(i, MG_USAGE_STACK_FREE), MG_ESC("total"),
-                      (size_t) mg_usage(i, MG_USAGE_STACK_TOTAL));
-  }
-  (void) ap;
-  return len + mg_xprintf(fn, arg, "]");
+static size_t print_mem_stat(mg_pfn_t fn, void *arg, const char *name,
+                             size_t free, size_t total) {
+  return mg_xprintf(fn, arg, "{%m:%m,%m:%zu,%m:%zu}", MG_ESC("name"),
+                    MG_ESC(name == NULL ? "" : name), MG_ESC("free"), free,
+                    MG_ESC("total"), total);
 }
 
 size_t mg_print_mem_stats(mg_pfn_t fn, void *arg, va_list *ap) {
-  size_t heap_total = (size_t) mg_usage(0, MG_USAGE_HEAP_TOTAL);
-  size_t heap_free = (size_t) mg_usage(0, MG_USAGE_HEAP_FREE);
+  int i, count;
+  size_t heap_total = mg_usage(0, MG_USAGE_HEAP_TOTAL);
+  size_t heap_free = mg_usage(0, MG_USAGE_HEAP_FREE);
+  size_t len = mg_xprintf(fn, arg, "[");
+  len += print_mem_stat(fn, arg, "heap", heap_free, heap_total);
+  count = (int) mg_usage(-1, MG_USAGE_NUM_TASKS);
+  for (i = 0; i < count; i++) {
+    const char *name = (const char *) mg_usage(i, MG_USAGE_TASK_NAME);
+    len += mg_xprintf(fn, arg, ",");
+    len += print_mem_stat(fn, arg, name, mg_usage(i, MG_USAGE_STACK_FREE),
+                          mg_usage(i, MG_USAGE_STACK_TOTAL));
+  }
   (void) ap;
-  return mg_xprintf(fn, arg, "{%m:%zu,%m:%zu,%m:%M}",
-                    MG_ESC("heap_total"), heap_total, MG_ESC("heap_free"),
-                    heap_free, MG_ESC("stacks"), print_stacks);
+  return len + mg_xprintf(fn, arg, "]");
 }
 
 #if MG_ARCH == MG_ARCH_ESP32
diff --git a/mongoose.h b/mongoose.h
index 480ec5f3..995d9476 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -4516,8 +4516,8 @@ size_t mg_usage(int task, int metric);
 
 #define MG_HEALTH_INIT() mg_health_init()
 extern size_t mg_print_crash_record(mg_pfn_t, void *, va_list *);
-// JSON memory statistics via mg_usage(), suitable for %M: heap_total, heap_free,
-// and a stacks array of {name, free, total}
+// JSON memory statistics via mg_usage(), suitable for %M: an array of
+// {name, free, total} entries, starting with "heap", then task stacks
 // A zero total means unknown
 extern size_t mg_print_mem_stats(mg_pfn_t, void *, va_list *);
 extern void mg_health_init(void);
@@ -4540,7 +4540,7 @@ static inline size_t mg_print_crash_record(mg_pfn_t fn, void *arg,
 }
 static inline size_t mg_print_mem_stats(mg_pfn_t fn, void *arg, va_list *ap) {
   (void) ap;
-  return mg_xprintf(fn, arg, "{}");
+  return mg_xprintf(fn, arg, "[]");
 }
 static inline bool mg_health_coredump_begin(size_t *size) {
   (void) size;
diff --git a/src/health.c b/src/health.c
index 2be84cfd..351fceda 100644
--- a/src/health.c
+++ b/src/health.c
@@ -58,29 +58,28 @@ size_t mg_usage(int task, int metric) {
 }
 #endif
 
-static size_t print_stacks(mg_pfn_t fn, void *arg, va_list *ap) {
-  int i;
-  int count = (int) mg_usage(-1, MG_USAGE_NUM_TASKS);
-  size_t len = mg_xprintf(fn, arg, "[");
-  for (i = 0; i < count; i++) {
-    const char *name = (const char *) mg_usage(i, MG_USAGE_TASK_NAME);
-    len += mg_xprintf(fn, arg, "%s{%m:%m,%m:%zu,%m:%zu}",
-                      i == 0 ? "" : ",", MG_ESC("name"),
-                      MG_ESC(name == NULL ? "" : name), MG_ESC("free"),
-                      (size_t) mg_usage(i, MG_USAGE_STACK_FREE), MG_ESC("total"),
-                      (size_t) mg_usage(i, MG_USAGE_STACK_TOTAL));
-  }
-  (void) ap;
-  return len + mg_xprintf(fn, arg, "]");
+static size_t print_mem_stat(mg_pfn_t fn, void *arg, const char *name,
+                             size_t free, size_t total) {
+  return mg_xprintf(fn, arg, "{%m:%m,%m:%zu,%m:%zu}", MG_ESC("name"),
+                    MG_ESC(name == NULL ? "" : name), MG_ESC("free"), free,
+                    MG_ESC("total"), total);
 }
 
 size_t mg_print_mem_stats(mg_pfn_t fn, void *arg, va_list *ap) {
-  size_t heap_total = (size_t) mg_usage(0, MG_USAGE_HEAP_TOTAL);
-  size_t heap_free = (size_t) mg_usage(0, MG_USAGE_HEAP_FREE);
+  int i, count;
+  size_t heap_total = mg_usage(0, MG_USAGE_HEAP_TOTAL);
+  size_t heap_free = mg_usage(0, MG_USAGE_HEAP_FREE);
+  size_t len = mg_xprintf(fn, arg, "[");
+  len += print_mem_stat(fn, arg, "heap", heap_free, heap_total);
+  count = (int) mg_usage(-1, MG_USAGE_NUM_TASKS);
+  for (i = 0; i < count; i++) {
+    const char *name = (const char *) mg_usage(i, MG_USAGE_TASK_NAME);
+    len += mg_xprintf(fn, arg, ",");
+    len += print_mem_stat(fn, arg, name, mg_usage(i, MG_USAGE_STACK_FREE),
+                          mg_usage(i, MG_USAGE_STACK_TOTAL));
+  }
   (void) ap;
-  return mg_xprintf(fn, arg, "{%m:%zu,%m:%zu,%m:%M}",
-                    MG_ESC("heap_total"), heap_total, MG_ESC("heap_free"),
-                    heap_free, MG_ESC("stacks"), print_stacks);
+  return len + mg_xprintf(fn, arg, "]");
 }
 
 #if MG_ARCH == MG_ARCH_ESP32
diff --git a/src/health.h b/src/health.h
index 112510de..e3c38291 100644
--- a/src/health.h
+++ b/src/health.h
@@ -139,8 +139,8 @@ size_t mg_usage(int task, int metric);
 
 #define MG_HEALTH_INIT() mg_health_init()
 extern size_t mg_print_crash_record(mg_pfn_t, void *, va_list *);
-// JSON memory statistics via mg_usage(), suitable for %M: heap_total, heap_free,
-// and a stacks array of {name, free, total}
+// JSON memory statistics via mg_usage(), suitable for %M: an array of
+// {name, free, total} entries, starting with "heap", then task stacks
 // A zero total means unknown
 extern size_t mg_print_mem_stats(mg_pfn_t, void *, va_list *);
 extern void mg_health_init(void);
@@ -163,7 +163,7 @@ static inline size_t mg_print_crash_record(mg_pfn_t fn, void *arg,
 }
 static inline size_t mg_print_mem_stats(mg_pfn_t fn, void *arg, va_list *ap) {
   (void) ap;
-  return mg_xprintf(fn, arg, "{}");
+  return mg_xprintf(fn, arg, "[]");
 }
 static inline bool mg_health_coredump_begin(size_t *size) {
   (void) size;