diff --git a/Python/ast.c b/Python/ast.c
index d00fcc8..9180fd0 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -638,8 +638,10 @@
                    anything other than EQUAL or a comma? */
                 /* XXX Should NCH(n) check be made a separate check? */
                 if (i + 1 < NCH(n) && TYPE(CHILD(n, i + 1)) == EQUAL) {
-                    asdl_seq_SET(defaults, j++, 
-				    ast_for_expr(c, CHILD(n, i + 2)));
+                    expr_ty expression = ast_for_expr(c, CHILD(n, i + 2));
+                    if (!expression)
+                            goto error;
+                    asdl_seq_SET(defaults, j++, expression);
                     i += 2;
 		    found_default = 1;
                 }
diff --git a/Python/compile.c b/Python/compile.c
index 8341cc9..3ee5cbb 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -1105,8 +1105,17 @@
 	u->u_name = name;
 	u->u_varnames = list2dict(u->u_ste->ste_varnames);
 	u->u_cellvars = dictbytype(u->u_ste->ste_symbols, CELL, 0, 0);
+	if (!u->u_varnames || !u->u_cellvars) {
+		compiler_unit_free(u);
+		return 0;
+	}
+
 	u->u_freevars = dictbytype(u->u_ste->ste_symbols, FREE, DEF_FREE_CLASS,
 				   PyDict_Size(u->u_cellvars));
+	if (!u->u_freevars) {
+		compiler_unit_free(u);
+		return 0;
+	}
 
 	u->u_blocks = NULL;
 	u->u_tmpname = 0;
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index 95a3372..bc83219 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -1204,8 +1204,12 @@
 {
 	PyObject *ret = NULL;
 	PyArena *arena = PyArena_New();
-	mod_ty mod = PyParser_ASTFromString(str, "<string>", start, flags,
-					    arena);
+	mod_ty mod;
+
+	if (arena == NULL)
+		return NULL;
+	
+	mod = PyParser_ASTFromString(str, "<string>", start, flags, arena);
 	if (mod != NULL)
 		ret = run_mod(mod, "<string>", globals, locals, flags, arena);
 	PyArena_Free(arena);
@@ -1218,8 +1222,13 @@
 {
 	PyObject *ret;
 	PyArena *arena = PyArena_New();
-	mod_ty mod = PyParser_ASTFromFile(fp, filename, start, 0, 0,
-					  flags, NULL, arena);
+	mod_ty mod;
+
+	if (arena == NULL)
+		return NULL;
+	
+	mod = PyParser_ASTFromFile(fp, filename, start, 0, 0,
+				   flags, NULL, arena);
 	if (mod == NULL) {
 		PyArena_Free(arena);
 		return NULL;
diff --git a/Python/symtable.c b/Python/symtable.c
index 1dc2a2e..fae9208 100644
--- a/Python/symtable.c
+++ b/Python/symtable.c
@@ -221,8 +221,12 @@
 		return st;
 	st->st_filename = filename;
 	st->st_future = future;
-	symtable_enter_block(st, GET_IDENTIFIER(top), ModuleBlock, 
-			     (void *)mod, 0);
+	if (!symtable_enter_block(st, GET_IDENTIFIER(top), ModuleBlock, 
+			     (void *)mod, 0)) {
+		PySymtable_Free(st);
+		return NULL;
+	}
+
 	st->st_top = st->st_cur;
 	st->st_cur->ste_unoptimized = OPT_TOPLEVEL;
 	/* Any other top-level initialization? */
@@ -728,6 +732,8 @@
 	if (end >= 0) {
 		st->st_cur = (PySTEntryObject *)PyList_GET_ITEM(st->st_stack, 
 								end);
+		if (st->st_cur == NULL)
+			return 0;
 		Py_INCREF(st->st_cur);
 		if (PySequence_DelItem(st->st_stack, end) < 0)
 			return 0;
@@ -749,6 +755,8 @@
 		Py_DECREF(st->st_cur);
 	}
 	st->st_cur = PySTEntry_New(st, name, block, ast, lineno);
+	if (st->st_cur == NULL)
+		return 0;
 	if (name == GET_IDENTIFIER(top))
 		st->st_global = st->st_cur->ste_symbols;
 	if (prev) {
diff --git a/Python/thread.c b/Python/thread.c
index bc501822..3a2c7af 100644
--- a/Python/thread.c
+++ b/Python/thread.c
@@ -267,6 +267,8 @@
 	struct key *p;
 	long id = PyThread_get_thread_ident();
 
+	if (!keymutex)
+		return NULL;
 	PyThread_acquire_lock(keymutex, 1);
 	for (p = keyhead; p != NULL; p = p->next) {
 		if (p->id == id && p->key == key)