diff --git a/examples/stm32/nucleo-f429zi-baremetal/syscalls.c b/examples/stm32/nucleo-f429zi-baremetal/syscalls.c
index be3210aa..ac27f093 100644
--- a/examples/stm32/nucleo-f429zi-baremetal/syscalls.c
+++ b/examples/stm32/nucleo-f429zi-baremetal/syscalls.c
@@ -12,8 +12,11 @@ void *_sbrk(int incr) {
   extern char _end;
   static unsigned char *heap = NULL;
   unsigned char *prev_heap;
+  unsigned char x = 0, *heap_end = (unsigned char *)((size_t) &x - 512);
+  (void) x;
   if (heap == NULL) heap = (unsigned char *) &_end;
   prev_heap = heap;
+  if (heap + incr > heap_end) return (void *) -1;
   heap += incr;
   return prev_heap;
 }
diff --git a/examples/stm32/nucleo-f429zi-rndis/syscalls.c b/examples/stm32/nucleo-f429zi-rndis/syscalls.c
index be3210aa..ac27f093 100644
--- a/examples/stm32/nucleo-f429zi-rndis/syscalls.c
+++ b/examples/stm32/nucleo-f429zi-rndis/syscalls.c
@@ -12,8 +12,11 @@ void *_sbrk(int incr) {
   extern char _end;
   static unsigned char *heap = NULL;
   unsigned char *prev_heap;
+  unsigned char x = 0, *heap_end = (unsigned char *)((size_t) &x - 512);
+  (void) x;
   if (heap == NULL) heap = (unsigned char *) &_end;
   prev_heap = heap;
+  if (heap + incr > heap_end) return (void *) -1;
   heap += incr;
   return prev_heap;
 }
diff --git a/examples/stm32/nucleo-f746zg-baremetal/syscalls.c b/examples/stm32/nucleo-f746zg-baremetal/syscalls.c
index be3210aa..ac27f093 100644
--- a/examples/stm32/nucleo-f746zg-baremetal/syscalls.c
+++ b/examples/stm32/nucleo-f746zg-baremetal/syscalls.c
@@ -12,8 +12,11 @@ void *_sbrk(int incr) {
   extern char _end;
   static unsigned char *heap = NULL;
   unsigned char *prev_heap;
+  unsigned char x = 0, *heap_end = (unsigned char *)((size_t) &x - 512);
+  (void) x;
   if (heap == NULL) heap = (unsigned char *) &_end;
   prev_heap = heap;
+  if (heap + incr > heap_end) return (void *) -1;
   heap += incr;
   return prev_heap;
 }
diff --git a/examples/stm32/nucleo-f746zg-rndis/syscalls.c b/examples/stm32/nucleo-f746zg-rndis/syscalls.c
index be3210aa..ac27f093 100644
--- a/examples/stm32/nucleo-f746zg-rndis/syscalls.c
+++ b/examples/stm32/nucleo-f746zg-rndis/syscalls.c
@@ -12,8 +12,11 @@ void *_sbrk(int incr) {
   extern char _end;
   static unsigned char *heap = NULL;
   unsigned char *prev_heap;
+  unsigned char x = 0, *heap_end = (unsigned char *)((size_t) &x - 512);
+  (void) x;
   if (heap == NULL) heap = (unsigned char *) &_end;
   prev_heap = heap;
+  if (heap + incr > heap_end) return (void *) -1;
   heap += incr;
   return prev_heap;
 }
diff --git a/examples/stm32/nucleo-h743zi-baremetal/syscalls.c b/examples/stm32/nucleo-h743zi-baremetal/syscalls.c
index be3210aa..ac27f093 100644
--- a/examples/stm32/nucleo-h743zi-baremetal/syscalls.c
+++ b/examples/stm32/nucleo-h743zi-baremetal/syscalls.c
@@ -12,8 +12,11 @@ void *_sbrk(int incr) {
   extern char _end;
   static unsigned char *heap = NULL;
   unsigned char *prev_heap;
+  unsigned char x = 0, *heap_end = (unsigned char *)((size_t) &x - 512);
+  (void) x;
   if (heap == NULL) heap = (unsigned char *) &_end;
   prev_heap = heap;
+  if (heap + incr > heap_end) return (void *) -1;
   heap += incr;
   return prev_heap;
 }