diff --git a/ports/unix/coverage.c b/ports/unix/coverage.c
index 2b65b47fc5..644e6927a8 100644
--- a/ports/unix/coverage.c
+++ b/ports/unix/coverage.c
@@ -292,6 +292,13 @@ static mp_obj_t extra_coverage(void) {
             gc_collect();
         }
 
+        // resize one of the blocks
+        void *before = ptrs[1];
+        ptrs[1] = FLIP_POINTER(m_tracked_realloc(FLIP_POINTER(ptrs[1]), 2 * NUM_BYTES));
+        void *after = ptrs[1];
+        bool location_changed = before != after;
+        mp_printf(&mp_plat_print, "%d\n", location_changed);
+
         // check the memory blocks have the correct content
         for (size_t i = 0; i < NUM_PTRS; ++i) {
             bool correct_contents = true;
diff --git a/py/malloc.c b/py/malloc.c
index f557ade44f..eb564cc516 100644
--- a/py/malloc.c
+++ b/py/malloc.c
@@ -263,6 +263,49 @@ void *m_tracked_calloc(size_t nmemb, size_t size) {
     return &node->data[0];
 }
 
+void *m_tracked_realloc(void *ptr_in, size_t n_bytes) {
+    // check for pure allocation
+    if (ptr_in == NULL) {
+        return m_tracked_calloc(1, n_bytes);
+    }
+    // check for pure free
+    if (n_bytes == 0) {
+        m_tracked_free(ptr_in);
+        return NULL;
+    }
+    m_tracked_node_t *node = (m_tracked_node_t *)((uint8_t *)ptr_in - sizeof(m_tracked_node_t));
+    #if MICROPY_MALLOC_USES_ALLOCATED_SIZE || MICROPY_DEBUG_VERBOSE
+    size_t prev_bytes;
+    #if MICROPY_TRACKED_ALLOC_STORE_SIZE
+    prev_bytes = node->size;
+    #else
+    prev_bytes = gc_nbytes(node);
+    #endif
+    #if MICROPY_DEBUG_VERBOSE
+    size_t nb;
+    size_t n = m_tracked_count_links(&nb);
+    DEBUG_printf("m_tracked_realloc(%p, [%p, %p], pbytes=%u, nbytes=%u, links=%u;%u)\n", node, node->prev, node->next, (int)prev_bytes, (int)n_bytes, (int)n, (int)nb);
+    #endif
+    #endif
+    node = m_realloc(node,
+        #if MICROPY_MALLOC_USES_ALLOCATED_SIZE
+        sizeof(m_tracked_node_t) + prev_bytes,
+        #endif
+        sizeof(m_tracked_node_t) + n_bytes
+        );
+    if (node == NULL) {
+        node->prev->next = node->next;
+        node->next->prev = node->prev;
+        return NULL;
+    }
+    #if MICROPY_TRACKED_ALLOC_STORE_SIZE
+    node->size = n_bytes;
+    #endif
+    node->prev->next = node;
+    node->next->prev = node;
+    return &node->data[0];
+}
+
 void m_tracked_free(void *ptr_in) {
     if (ptr_in == NULL) {
         return;
diff --git a/py/misc.h b/py/misc.h
index 96b13c151a..3b52945be7 100644
--- a/py/misc.h
+++ b/py/misc.h
@@ -111,6 +111,7 @@ NORETURN void m_malloc_fail(size_t num_bytes);
 // These alloc/free functions track the pointers in a linked list so the GC does not reclaim
 // them.  They can be used by code that requires traditional C malloc/free semantics.
 void *m_tracked_calloc(size_t nmemb, size_t size);
+void *m_tracked_realloc(void *ptr_in, size_t n_bytes);
 void m_tracked_free(void *ptr_in);
 #endif
 
diff --git a/tests/ports/unix/extra_coverage.py.exp b/tests/ports/unix/extra_coverage.py.exp
index 176db8e9f8..91aa33080b 100644
--- a/tests/ports/unix/extra_coverage.py.exp
+++ b/tests/ports/unix/extra_coverage.py.exp
@@ -29,6 +29,7 @@ m_tracked_head = 0
 5 1
 6 1
 7 1
+1
 0 1
 1 1
 2 1
diff --git a/tests/run-tests.py b/tests/run-tests.py
index f9f8413077..c0ab1dc932 100755
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -937,6 +937,10 @@ the last matching regex is used:
   run-tests.py -i async - exclude all, then include tests containing "async" anywhere
   run-tests.py -e '/big.+int' - include all, then exclude by regex
   run-tests.py -e async -i async_foo - include all, exclude async, yet still include async_foo
+
+For tests that use cpython, unix micropython and mpy-cross, the default executables
+vcan be overridden with the environment variables MICROPY_CPYTHON3, MICROPY_MICROPYTHON and
+MICROPY_MPYCROSS respectively.
 """,
     )
     cmd_parser.add_argument("--target", default="unix", help="the target platform")