diff --git a/chibicc.h b/chibicc.h
index 2b8883b..9ec8887 100644
--- a/chibicc.h
+++ b/chibicc.h
@@ -4,6 +4,7 @@
 #include <errno.h>
 #include <stdarg.h>
 #include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -37,7 +38,7 @@ typedef struct Token Token;
 struct Token {
   TokenKind kind; // Token kind
   Token *next;    // Next token
-  int val;        // If kind is TK_NUM, its value
+  int64_t val;    // If kind is TK_NUM, its value
   char *loc;      // Token location
   int len;        // Token length
   Type *ty;       // Used if TK_STR
@@ -140,7 +141,7 @@ struct Node {
   Node *args;
 
   Obj *var;      // Used if kind == ND_VAR
-  int val;       // Used if kind == ND_NUM
+  int64_t val;   // Used if kind == ND_NUM
 };
 
 Obj *parse(Token *tok);
@@ -152,6 +153,7 @@ Obj *parse(Token *tok);
 typedef enum {
   TY_CHAR,
   TY_INT,
+  TY_LONG,
   TY_PTR,
   TY_FUNC,
   TY_ARRAY,
@@ -199,6 +201,7 @@ struct Member {
 
 extern Type *ty_char;
 extern Type *ty_int;
+extern Type *ty_long;
 
 bool is_integer(Type *ty);
 Type *copy_type(Type *ty);
diff --git a/codegen.c b/codegen.c
index 30574ab..d77dfda 100644
--- a/codegen.c
+++ b/codegen.c
@@ -114,7 +114,7 @@ static void gen_expr(Node *node) {
 
   switch (node->kind) {
   case ND_NUM:
-    println("  mov $%d, %%rax", node->val);
+    println("  mov $%ld, %%rax", node->val);
     return;
   case ND_NEG:
     gen_expr(node->lhs);
diff --git a/parse.c b/parse.c
index f1c4b20..bfe5f4d 100644
--- a/parse.c
+++ b/parse.c
@@ -119,7 +119,7 @@ static Node *new_unary(NodeKind kind, Node *expr, Token *tok) {
   return node;
 }
 
-static Node *new_num(int val, Token *tok) {
+static Node *new_num(int64_t val, Token *tok) {
   Node *node = new_node(ND_NUM, tok);
   node->val = val;
   return node;
@@ -198,7 +198,7 @@ static void push_tag_scope(Token *tok, Type *ty) {
   scope->tags = sc;
 }
 
-// declspec = "char" | "int" | struct-decl
+// declspec = "char" | "short" | "int" | "long" | struct-decl | union-decl
 static Type *declspec(Token **rest, Token *tok) {
   if (equal(tok, "char")) {
     *rest = tok->next;
@@ -210,6 +210,11 @@ static Type *declspec(Token **rest, Token *tok) {
     return ty_int;
   }
 
+  if (equal(tok, "long")) {
+    *rest = tok->next;
+    return ty_long;
+  }
+
   if (equal(tok, "struct"))
     return struct_decl(rest, tok->next);
 
@@ -301,8 +306,8 @@ static Node *declaration(Token **rest, Token *tok) {
 
 // Returns true if a given token represents a type.
 static bool is_typename(Token *tok) {
-  return equal(tok, "char") || equal(tok, "int") || equal(tok, "struct") ||
-         equal(tok, "union");
+  return equal(tok, "char") || equal(tok, "short") || equal(tok, "int") ||
+         equal(tok, "long") || equal(tok, "struct") || equal(tok, "union");
 }
 
 // stmt = "return" expr ";"
diff --git a/test/function.c b/test/function.c
index 39fff11..951a281 100644
--- a/test/function.c
+++ b/test/function.c
@@ -31,6 +31,10 @@ int fib(int x) {
   return fib(x-1) + fib(x-2);
 }
 
+int sub_long(long a, long b, long c) {
+  return a - b - c;
+}
+
 int main() {
   ASSERT(3, ret3());
   ASSERT(8, add2(3, 5));
@@ -45,6 +49,8 @@ int main() {
 
   ASSERT(1, ({ sub_char(7, 3, 3); }));
 
+  ASSERT(1, sub_long(7, 3, 3));
+
   printf("OK\n");
   return 0;
 }
diff --git a/test/struct.c b/test/struct.c
index 8975f43..7ca0374 100644
--- a/test/struct.c
+++ b/test/struct.c
@@ -49,6 +49,8 @@ int main() {
   ASSERT(8, ({ struct t {int a; int b;} x; struct t y; sizeof(y); }));
   ASSERT(8, ({ struct t {int a; int b;}; struct t y; sizeof(y); }));
 
+  ASSERT(16, ({ struct {char a; long b;} x; sizeof(x); }));
+
   printf("OK\n");
   return 0;
 }
diff --git a/test/variable.c b/test/variable.c
index ee8e4ee..a329a9a 100644
--- a/test/variable.c
+++ b/test/variable.c
@@ -50,6 +50,8 @@ int main() {
   ASSERT(7, ({ int x; int y; char z; char *a=&y; char *b=&z; b-a; }));
   ASSERT(1, ({ int x; char y; int z; char *a=&y; char *b=&z; b-a; }));
 
+  ASSERT(8, ({ long x; sizeof(x); }));
+
   printf("OK\n");
   return 0;
 }
diff --git a/tokenize.c b/tokenize.c
index 4c29bc2..3224369 100644
--- a/tokenize.c
+++ b/tokenize.c
@@ -126,7 +126,7 @@ static int read_punct(char *p) {
 static bool is_keyword(Token *tok) {
   static char *kw[] = {
     "return", "if", "else", "for", "while", "int", "sizeof", "char",
-    "struct", "union",
+    "struct", "union", "short", "long",
   };
 
   for (int i = 0; i < sizeof(kw) / sizeof(*kw); i++)
diff --git a/type.c b/type.c
index e5baf1f..18c6e9d 100644
--- a/type.c
+++ b/type.c
@@ -2,6 +2,7 @@
 
 Type *ty_char = &(Type){TY_CHAR, 1, 1};
 Type *ty_int = &(Type){TY_INT, 4, 4};
+Type *ty_long = &(Type){TY_LONG, 8, 8};
 
 static Type *new_type(TypeKind kind, int size, int align) {
   Type *ty = calloc(1, sizeof(Type));
@@ -12,7 +13,8 @@ static Type *new_type(TypeKind kind, int size, int align) {
 }
 
 bool is_integer(Type *ty) {
-  return ty->kind == TY_CHAR || ty->kind == TY_INT;
+  TypeKind k = ty->kind;
+  return k == TY_CHAR || k == TY_INT || k == TY_LONG;
 }
 
 Type *copy_type(Type *ty) {
@@ -77,7 +79,7 @@ void add_type(Node *node) {
   case ND_LE:
   case ND_NUM:
   case ND_FUNCALL:
-    node->ty = ty_int;
+    node->ty = ty_long;
     return;
   case ND_VAR:
     node->ty = node->var->ty;