diff --git a/src/tint/reader/wgsl/lexer.cc b/src/tint/reader/wgsl/lexer.cc
index 122fcda93e..e7a3a4b782 100644
--- a/src/tint/reader/wgsl/lexer.cc
+++ b/src/tint/reader/wgsl/lexer.cc
@@ -681,7 +681,13 @@ Token Lexer::build_token_from_int_if_possible(Source source,
                                               size_t end,
                                               int32_t base) {
   auto res = strtoll(&at(start), nullptr, base);
+
   if (matches(pos(), "u")) {
+    if (res < 0) {
+      return {Token::Type::kError, source,
+              "u32 (" + std::string{substr(start, end - start)} +
+                  ") must not be negative"};
+    }
     if (static_cast<uint64_t>(res) >
         static_cast<uint64_t>(std::numeric_limits<uint32_t>::max())) {
       return {
@@ -693,6 +699,10 @@ Token Lexer::build_token_from_int_if_possible(Source source,
     return {source, static_cast<uint32_t>(res)};
   }
 
+  if (matches(pos(), "i")) {
+    advance(1);
+  }
+
   if (res < static_cast<int64_t>(std::numeric_limits<int32_t>::min())) {
     return {Token::Type::kError, source,
             "i32 (" + std::string{substr(start, end - start)} + ") too small"};
diff --git a/src/tint/reader/wgsl/parser_impl_const_literal_test.cc b/src/tint/reader/wgsl/parser_impl_const_literal_test.cc
index 44c70832b4..e5cf61b668 100644
--- a/src/tint/reader/wgsl/parser_impl_const_literal_test.cc
+++ b/src/tint/reader/wgsl/parser_impl_const_literal_test.cc
@@ -42,15 +42,50 @@ float MakeFloat(int sign, int biased_exponent, int mantissa) {
 }
 
 TEST_F(ParserImplTest, ConstLiteral_Int) {
-  auto p = parser("-234");
-  auto c = p->const_literal();
-  EXPECT_TRUE(c.matched);
-  EXPECT_FALSE(c.errored);
-  EXPECT_FALSE(p->has_error()) << p->error();
-  ASSERT_NE(c.value, nullptr);
-  ASSERT_TRUE(c->Is<ast::SintLiteralExpression>());
-  EXPECT_EQ(c->As<ast::SintLiteralExpression>()->value, -234);
-  EXPECT_EQ(c->source.range, (Source::Range{{1u, 1u}, {1u, 5u}}));
+  {
+    auto p = parser("234");
+    auto c = p->const_literal();
+    EXPECT_TRUE(c.matched);
+    EXPECT_FALSE(c.errored);
+    EXPECT_FALSE(p->has_error()) << p->error();
+    ASSERT_NE(c.value, nullptr);
+    ASSERT_TRUE(c->Is<ast::SintLiteralExpression>());
+    EXPECT_EQ(c->As<ast::SintLiteralExpression>()->value, 234);
+    EXPECT_EQ(c->source.range, (Source::Range{{1u, 1u}, {1u, 4u}}));
+  }
+  {
+    auto p = parser("234i");
+    auto c = p->const_literal();
+    EXPECT_TRUE(c.matched);
+    EXPECT_FALSE(c.errored);
+    EXPECT_FALSE(p->has_error()) << p->error();
+    ASSERT_NE(c.value, nullptr);
+    ASSERT_TRUE(c->Is<ast::SintLiteralExpression>());
+    EXPECT_EQ(c->As<ast::SintLiteralExpression>()->value, 234);
+    EXPECT_EQ(c->source.range, (Source::Range{{1u, 1u}, {1u, 5u}}));
+  }
+  {
+    auto p = parser("-234");
+    auto c = p->const_literal();
+    EXPECT_TRUE(c.matched);
+    EXPECT_FALSE(c.errored);
+    EXPECT_FALSE(p->has_error()) << p->error();
+    ASSERT_NE(c.value, nullptr);
+    ASSERT_TRUE(c->Is<ast::SintLiteralExpression>());
+    EXPECT_EQ(c->As<ast::SintLiteralExpression>()->value, -234);
+    EXPECT_EQ(c->source.range, (Source::Range{{1u, 1u}, {1u, 5u}}));
+  }
+  {
+    auto p = parser("-234i");
+    auto c = p->const_literal();
+    EXPECT_TRUE(c.matched);
+    EXPECT_FALSE(c.errored);
+    EXPECT_FALSE(p->has_error()) << p->error();
+    ASSERT_NE(c.value, nullptr);
+    ASSERT_TRUE(c->Is<ast::SintLiteralExpression>());
+    EXPECT_EQ(c->As<ast::SintLiteralExpression>()->value, -234);
+    EXPECT_EQ(c->source.range, (Source::Range{{1u, 1u}, {1u, 6u}}));
+  }
 }
 
 TEST_F(ParserImplTest, ConstLiteral_Uint) {
@@ -65,6 +100,15 @@ TEST_F(ParserImplTest, ConstLiteral_Uint) {
   EXPECT_EQ(c->source.range, (Source::Range{{1u, 1u}, {1u, 5u}}));
 }
 
+TEST_F(ParserImplTest, ConstLiteral_Uint_Negative) {
+  auto p = parser("-234u");
+  auto c = p->const_literal();
+  EXPECT_FALSE(c.matched);
+  EXPECT_TRUE(c.errored);
+  EXPECT_EQ(p->error(), "1:1: u32 (-234) must not be negative");
+  ASSERT_EQ(c.value, nullptr);
+}
+
 TEST_F(ParserImplTest, ConstLiteral_Float) {
   auto p = parser("234.e12");
   auto c = p->const_literal();