diff --git a/cores/esp8266/abi.cpp b/cores/esp8266/abi.cpp
index 2670ec989..8001c185a 100644
--- a/cores/esp8266/abi.cpp
+++ b/cores/esp8266/abi.cpp
@@ -24,14 +24,28 @@
 
 using __cxxabiv1::__guard;
 
+// Debugging helper, last allocation which returned NULL
+extern void *umm_last_fail_alloc_addr;
+extern int umm_last_fail_alloc_size;
+
 void *operator new(size_t size)
 {
-    return malloc(size);
+    void *ret = malloc(size);
+    if (0 != size && 0 == ret) {
+        umm_last_fail_alloc_addr = __builtin_return_address(0);
+        umm_last_fail_alloc_size = size;
+    }
+    return ret;
 }
 
 void *operator new[](size_t size)
 {
-    return malloc(size);
+    void *ret = malloc(size);
+    if (0 != size && 0 == ret) {
+        umm_last_fail_alloc_addr = __builtin_return_address(0);
+        umm_last_fail_alloc_size = size;
+    }
+    return ret;
 }
 
 void operator delete(void * ptr)
diff --git a/cores/esp8266/core_esp8266_postmortem.c b/cores/esp8266/core_esp8266_postmortem.c
index 971242979..fc47f4f03 100644
--- a/cores/esp8266/core_esp8266_postmortem.c
+++ b/cores/esp8266/core_esp8266_postmortem.c
@@ -45,6 +45,11 @@ static void uart_write_char_d(char c);
 static void uart0_write_char_d(char c);
 static void uart1_write_char_d(char c);
 static void print_stack(uint32_t start, uint32_t end);
+
+// From UMM, the last caller of a malloc/realloc/calloc which failed:
+extern void *umm_last_fail_alloc_addr;
+extern int umm_last_fail_alloc_size;
+
 static void raise_exception() __attribute__((noreturn));
 
 extern void __custom_crash_callback( struct rst_info * rst_info, uint32_t stack, uint32_t stack_end ) {
@@ -137,6 +142,11 @@ void __wrap_system_restart_local() {
 
     print_stack(sp + offset, stack_end);
 
+    // Use cap-X formatting to ensure the standard EspExceptionDecoder doesn't match the address
+    if (umm_last_fail_alloc_addr) {
+      ets_printf("\nlast failed alloc call: %08X(%d)\n", (uint32_t)umm_last_fail_alloc_addr, umm_last_fail_alloc_size);
+    }
+
     custom_crash_callback( &rst_info, sp + offset, stack_end );
 
     delayMicroseconds(10000);
diff --git a/cores/esp8266/heap.c b/cores/esp8266/heap.c
index 49b6f1258..5f5aaef79 100644
--- a/cores/esp8266/heap.c
+++ b/cores/esp8266/heap.c
@@ -8,10 +8,19 @@
 #include <c_types.h>
 #include <sys/reent.h>
 
+// Debugging helper, last allocation which returned NULL
+void *umm_last_fail_alloc_addr = NULL;
+int umm_last_fail_alloc_size = 0;
+
 void* _malloc_r(struct _reent* unused, size_t size)
 {
     (void) unused;
-    return malloc(size);
+    void *ret = malloc(size);
+    if (0 != size && 0 == ret) {
+        umm_last_fail_alloc_addr = __builtin_return_address(0);
+        umm_last_fail_alloc_size = size;
+    }
+    return ret;
 }
 
 void _free_r(struct _reent* unused, void* ptr)
@@ -23,13 +32,23 @@ void _free_r(struct _reent* unused, void* ptr)
 void* _realloc_r(struct _reent* unused, void* ptr, size_t size)
 {
     (void) unused;
-    return realloc(ptr, size);
+    void *ret = realloc(ptr, size);
+    if (0 != size && 0 == ret) {
+        umm_last_fail_alloc_addr = __builtin_return_address(0);
+        umm_last_fail_alloc_size = size;
+    }
+    return ret;
 }
 
 void* _calloc_r(struct _reent* unused, size_t count, size_t size)
 {
     (void) unused;
-    return calloc(count, size);
+    void *ret = calloc(count, size);
+    if (0 != (count * size) && 0 == ret) {
+        umm_last_fail_alloc_addr = __builtin_return_address(0);
+        umm_last_fail_alloc_size = count * size;
+    }
+    return ret;
 }
 
 void ICACHE_RAM_ATTR vPortFree(void *ptr, const char* file, int line)
diff --git a/cores/esp8266/umm_malloc/umm_malloc.c b/cores/esp8266/umm_malloc/umm_malloc.c
index ac249b643..d65eac781 100644
--- a/cores/esp8266/umm_malloc/umm_malloc.c
+++ b/cores/esp8266/umm_malloc/umm_malloc.c
@@ -499,6 +499,10 @@
 
 #include "umm_malloc_cfg.h"   /* user-dependent */
 
+// From UMM, the last caller of a malloc/realloc/calloc which failed:
+extern void *umm_last_fail_alloc_addr;
+extern int umm_last_fail_alloc_size;
+
 #ifndef UMM_FIRST_FIT
 #  ifndef UMM_BEST_FIT
 #    define UMM_BEST_FIT
@@ -1661,6 +1665,10 @@ void *umm_malloc( size_t size ) {
   size += POISON_SIZE(size);
 
   ret = _umm_malloc( size );
+  if (0 != size && 0 == ret) {
+    umm_last_fail_alloc_addr = __builtin_return_address(0);
+    umm_last_fail_alloc_size = size;
+  }
 
   ret = GET_POISONED(ret, size);
 
@@ -1688,6 +1696,10 @@ void *umm_calloc( size_t num, size_t item_size ) {
   if (ret) {
     memset(ret, 0x00, size);
   }
+  if (0 != size && 0 == ret) {
+    umm_last_fail_alloc_addr = __builtin_return_address(0);
+    umm_last_fail_alloc_size = size;
+  }
 
   ret = GET_POISONED(ret, size);
 
@@ -1713,6 +1725,10 @@ void *umm_realloc( void *ptr, size_t size ) {
 
   size += POISON_SIZE(size);
   ret = _umm_realloc( ptr, size );
+  if (0 != size && 0 == ret) {
+    umm_last_fail_alloc_addr = __builtin_return_address(0);
+    umm_last_fail_alloc_size = size;
+  }
 
   ret = GET_POISONED(ret, size);