diff --git a/src/core/array.c b/src/core/array.c
index 43bec654..c8ebcc58 100644
--- a/src/core/array.c
+++ b/src/core/array.c
@@ -34,7 +34,7 @@ static void janet_array_impl(JanetArray *array, int32_t capacity) {
     Janet *data = NULL;
     if (capacity > 0) {
         janet_vm.next_collection += capacity * sizeof(Janet);
-        data = (Janet *) janet_malloc(sizeof(Janet) * (size_t) capacity);
+        data = (Janet *) array_allocate(sizeof(Janet), capacity);
         if (NULL == data) {
             JANET_OUT_OF_MEMORY;
         }
@@ -63,7 +63,7 @@ JanetArray *janet_array_n(const Janet *elements, int32_t n) {
     JanetArray *array = janet_gcalloc(JANET_MEMORY_ARRAY, sizeof(JanetArray));
     array->capacity = n;
     array->count = n;
-    array->data = janet_malloc(sizeof(Janet) * (size_t) n);
+    array->data = array_allocate(sizeof(Janet), (size_t) n);
     if (!array->data) {
         JANET_OUT_OF_MEMORY;
     }
diff --git a/src/core/asm.c b/src/core/asm.c
index a563d633..9ab269cc 100644
--- a/src/core/asm.c
+++ b/src/core/asm.c
@@ -603,7 +603,7 @@ static JanetAssembleResult janet_asm1(JanetAssembler *parent, Janet source, int
     x = janet_get1(s, janet_ckeywordv("constants"));
     if (janet_indexed_view(x, &arr, &count)) {
         def->constants_length = count;
-        def->constants = janet_malloc(sizeof(Janet) * (size_t) count);
+        def->constants = array_allocate(sizeof(Janet), count);
         if (NULL == def->constants) {
             JANET_OUT_OF_MEMORY;
         }
@@ -667,7 +667,7 @@ static JanetAssembleResult janet_asm1(JanetAssembler *parent, Janet source, int
         }
         /* Allocate bytecode array */
         def->bytecode_length = blength;
-        def->bytecode = janet_malloc(sizeof(uint32_t) * (size_t) blength);
+        def->bytecode = array_allocate(sizeof(uint32_t), blength);
         if (NULL == def->bytecode) {
             JANET_OUT_OF_MEMORY;
         }
diff --git a/src/core/buffer.c b/src/core/buffer.c
index e8c1e85b..5a1e08b2 100644
--- a/src/core/buffer.c
+++ b/src/core/buffer.c
@@ -40,7 +40,7 @@ static JanetBuffer *janet_buffer_init_impl(JanetBuffer *buffer, int32_t capacity
     uint8_t *data = NULL;
     if (capacity < 4) capacity = 4;
     janet_gcpressure(capacity);
-    data = janet_malloc(sizeof(uint8_t) * (size_t) capacity);
+    data = array_allocate(sizeof(uint8_t), capacity);
     if (NULL == data) {
         JANET_OUT_OF_MEMORY;
     }
diff --git a/src/core/bytecode.c b/src/core/bytecode.c
index 8424efd6..f1fbbe1d 100644
--- a/src/core/bytecode.c
+++ b/src/core/bytecode.c
@@ -408,6 +408,7 @@ int janet_verify(JanetFuncDef *def) {
     int32_t maxslot = def->arity + vargs;
     int32_t sc = def->slotcount;
 
+    if (def->environments_length > 256) return 15;
     if (def->bytecode_length == 0) return 1;
 
     if (maxslot > sc) return 2;
diff --git a/src/core/fiber.c b/src/core/fiber.c
index f70a2683..9751b449 100644
--- a/src/core/fiber.c
+++ b/src/core/fiber.c
@@ -55,7 +55,7 @@ static JanetFiber *fiber_alloc(int32_t capacity) {
         capacity = 32;
     }
     fiber->capacity = capacity;
-    data = janet_malloc(sizeof(Janet) * (size_t) capacity);
+    data = array_allocate(sizeof(Janet), capacity);
     if (NULL == data) {
         JANET_OUT_OF_MEMORY;
     }
@@ -102,7 +102,7 @@ JanetFiber *janet_fiber(JanetFunction *callee, int32_t capacity, int32_t argc, c
 static void janet_fiber_refresh_memory(JanetFiber *fiber) {
     int32_t n = fiber->capacity;
     if (n) {
-        Janet *newData = janet_malloc(sizeof(Janet) * n);
+        Janet *newData = array_allocate(sizeof(Janet), n);
         if (NULL == newData) {
             JANET_OUT_OF_MEMORY;
         }
@@ -256,7 +256,7 @@ static void janet_env_detach(JanetFuncEnv *env) {
     /* Check for closure environment */
     if (env) {
         janet_env_valid(env);
-        int32_t len = env->length;
+        int32_t len = env->length; /* Maximum is 256 */
         size_t s = sizeof(Janet) * (size_t) len;
         Janet *vmem = janet_malloc(s);
         janet_vm.next_collection += (uint32_t) s;
diff --git a/src/core/marsh.c b/src/core/marsh.c
index 33a5f4d9..043fa8c1 100644
--- a/src/core/marsh.c
+++ b/src/core/marsh.c
@@ -79,13 +79,6 @@ enum {
     LB_ARRAY_WEAK, /* 232 */
 } LeadBytes;
 
-/* Avoid overflow and underflow, especially on 32-bit systems */
-static void *array_allocate(size_t element_size, int32_t count) {
-    if (count < 0) return NULL;
-    if ((size_t) count > (SIZE_MAX / element_size)) return NULL;
-    return janet_malloc(element_size * count);
-}
-
 /* Helper to look inside an entry in an environment */
 static Janet entry_getval(Janet env_entry) {
     if (janet_checktype(env_entry, JANET_TABLE)) {
diff --git a/src/core/table.c b/src/core/table.c
index 1cddad73..4ab6e6fb 100644
--- a/src/core/table.c
+++ b/src/core/table.c
@@ -260,7 +260,7 @@ JanetTable *janet_table_clone(JanetTable *table) {
     newTable->capacity = table->capacity;
     newTable->deleted = table->deleted;
     newTable->proto = table->proto;
-    newTable->data = janet_malloc(newTable->capacity * sizeof(JanetKV));
+    newTable->data = array_allocate(sizeof(JanetKV), newTable->capacity);
     if (NULL == newTable->data) {
         JANET_OUT_OF_MEMORY;
     }
diff --git a/src/core/util.c b/src/core/util.c
index 90e9a601..1156081e 100644
--- a/src/core/util.c
+++ b/src/core/util.c
@@ -1213,3 +1213,10 @@ void *(janet_calloc)(size_t nmemb, size_t size) {
 void *(janet_realloc)(void *ptr, size_t size) {
     return janet_realloc(ptr, size);
 }
+
+/* Avoid overflow and underflow, especially on 32-bit systems */
+void *array_allocate(size_t element_size, int32_t count) {
+    if (count < 0) return NULL;
+    if ((size_t) count > (SIZE_MAX / element_size)) return NULL;
+    return janet_malloc(element_size * count);
+}
diff --git a/src/core/util.h b/src/core/util.h
index d0adc0dd..101fc27d 100644
--- a/src/core/util.h
+++ b/src/core/util.h
@@ -172,6 +172,9 @@ int janet_gettime(struct timespec *spec, enum JanetTimeSource source);
 #define strdup(x) _strdup(x)
 #endif
 
+/* Safely allocate arrays */
+void *array_allocate(size_t element_size, int32_t count);
+
 /* Use LoadLibrary on windows or dlopen on posix to load dynamic libraries
  * with native code. */
 #if defined(JANET_NO_DYNAMIC_MODULES)
diff --git a/src/core/wrap.c b/src/core/wrap.c
index d44620e9..f3ab4dd4 100644
--- a/src/core/wrap.c
+++ b/src/core/wrap.c
@@ -162,7 +162,7 @@ Janet(janet_wrap_number)(double x) {
 
 void *janet_memalloc_empty(int32_t count) {
     int32_t i;
-    void *mem = janet_malloc((size_t) count * sizeof(JanetKV));
+    void *mem = array_allocate(sizeof(JanetKV), count);
     janet_vm.next_collection += (size_t) count * sizeof(JanetKV);
     if (NULL == mem) {
         JANET_OUT_OF_MEMORY;