diff --git a/Python/asdl.c b/Python/asdl.c
index 72329b9..1105d3a 100644
--- a/Python/asdl.c
+++ b/Python/asdl.c
@@ -5,8 +5,22 @@
 asdl_seq_new(int size, PyArena *arena)
 {
 	asdl_seq *seq = NULL;
-	size_t n = sizeof(asdl_seq) +
-			(size ? (sizeof(void *) * (size - 1)) : 0);
+	size_t n = (size ? (sizeof(void *) * (size - 1)) : 0);
+
+	/* check size is sane */
+	if (size < 0 || size == INT_MIN || 
+		(size && ((size - 1) > (PY_SIZE_MAX / sizeof(void *))))) {
+		PyErr_NoMemory();
+		return NULL;
+	}
+
+	/* check if size can be added safely */
+	if (n > PY_SIZE_MAX - sizeof(asdl_seq)) {
+		PyErr_NoMemory();
+		return NULL;
+	}
+
+	n += sizeof(asdl_seq);
 
 	seq = (asdl_seq *)PyArena_Malloc(arena, n);
 	if (!seq) {
@@ -22,8 +36,22 @@
 asdl_int_seq_new(int size, PyArena *arena)
 {
 	asdl_int_seq *seq = NULL;
-	size_t n = sizeof(asdl_seq) +
-			(size ? (sizeof(int) * (size - 1)) : 0);
+	size_t n = (size ? (sizeof(void *) * (size - 1)) : 0);
+
+	/* check size is sane */
+	if (size < 0 || size == INT_MIN || 
+		(size && ((size - 1) > (PY_SIZE_MAX / sizeof(void *))))) {
+			PyErr_NoMemory();
+			return NULL;
+	}
+
+	/* check if size can be added safely */
+	if (n > PY_SIZE_MAX - sizeof(asdl_seq)) {
+		PyErr_NoMemory();
+		return NULL;
+	}
+
+	n += sizeof(asdl_seq);
 
 	seq = (asdl_int_seq *)PyArena_Malloc(arena, n);
 	if (!seq) {
diff --git a/Python/ast.c b/Python/ast.c
index da42a0e..79c9403 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -3145,6 +3145,9 @@
         buf = (char *)s;
         u = NULL;
     } else {
+        /* check for integer overflow */
+        if (len > PY_SIZE_MAX / 4)
+            return NULL;
         /* "\XX" may become "\u005c\uHHLL" (12 bytes) */
         u = PyBytes_FromStringAndSize((char *)NULL, len * 4);
         if (u == NULL)
diff --git a/Python/compile.c b/Python/compile.c
index 6017b2c..942ca1f52 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -227,6 +227,10 @@
 		return ident; /* Don't mangle if class is just underscores */
 	}
 	plen = Py_UNICODE_strlen(p);
+
+	assert(1 <= PY_SSIZE_T_MAX - nlen);
+	assert(1 + nlen <= PY_SSIZE_T_MAX - plen);
+
 	ident = PyUnicode_FromStringAndSize(NULL, 1 + nlen + plen);
 	if (!ident)
 		return 0;
@@ -635,6 +639,12 @@
 		size_t oldsize, newsize;
 		oldsize = b->b_ialloc * sizeof(struct instr);
 		newsize = oldsize << 1;
+
+		if (oldsize > (PY_SIZE_MAX >> 1)) {
+			PyErr_NoMemory();
+			return -1;
+		}
+
 		if (newsize == 0) {
 			PyErr_NoMemory();
 			return -1;
@@ -3711,6 +3721,10 @@
 	a->a_lnotab = PyBytes_FromStringAndSize(NULL, DEFAULT_LNOTAB_SIZE);
 	if (!a->a_lnotab)
 		return 0;
+	if (nblocks > PY_SIZE_MAX / sizeof(basicblock *)) {
+		PyErr_NoMemory();
+		return 0;
+	}
 	a->a_postorder = (basicblock **)PyObject_Malloc(
 					    sizeof(basicblock *) * nblocks);
 	if (!a->a_postorder) {
@@ -3819,10 +3833,14 @@
 		nbytes = a->a_lnotab_off + 2 * ncodes;
 		len = PyBytes_GET_SIZE(a->a_lnotab);
 		if (nbytes >= len) {
-			if (len * 2 < nbytes)
+			if ((len <= INT_MAX / 2) && (len * 2 < nbytes))
 				len = nbytes;
-			else
+			else if (len <= INT_MAX / 2)
 				len *= 2;
+			else {
+				PyErr_NoMemory();
+				return 0;
+			}
 			if (_PyBytes_Resize(&a->a_lnotab, len) < 0)
 				return 0;
 		}
@@ -3841,10 +3859,14 @@
 		nbytes = a->a_lnotab_off + 2 * ncodes;
 		len = PyBytes_GET_SIZE(a->a_lnotab);
 		if (nbytes >= len) {
-			if (len * 2 < nbytes)
+			if ((len <= INT_MAX / 2) && len * 2 < nbytes)
 				len = nbytes;
-			else
+			else if (len <= INT_MAX / 2)
 				len *= 2;
+			else {
+				PyErr_NoMemory();
+				return 0;
+			}
 			if (_PyBytes_Resize(&a->a_lnotab, len) < 0)
 				return 0;
 		}
@@ -3903,6 +3925,8 @@
 	if (i->i_lineno && !assemble_lnotab(a, i))
 		return 0;
 	if (a->a_offset + size >= len) {
+		if (len > PY_SSIZE_T_MAX / 2)
+			return 0;
 		if (_PyBytes_Resize(&a->a_bytecode, len * 2) < 0)
 		    return 0;
 	}