diff --git a/tests/src/ip_address_test.cpp b/tests/src/ip_address_test.cpp
index e43b186..2be5701 100644
--- a/tests/src/ip_address_test.cpp
+++ b/tests/src/ip_address_test.cpp
@@ -113,6 +113,6 @@ TEST(IPAddressTest, Mask) {
 }
 
 TEST(IPv4AddressTest, Size) {
-    EXPECT_EQ(4, IPv4Address("127.0.0.1").size());
-    EXPECT_EQ(4, IPv4Address().size());
+    EXPECT_EQ(4UL, IPv4Address("127.0.0.1").size());
+    EXPECT_EQ(4UL, IPv4Address().size());
 }
diff --git a/tests/src/ipv6_address_test.cpp b/tests/src/ipv6_address_test.cpp
index 50a77f8..5f8fa16 100644
--- a/tests/src/ipv6_address_test.cpp
+++ b/tests/src/ipv6_address_test.cpp
@@ -125,8 +125,8 @@ TEST(IPv6AddressTest, MaskAddress) {
 }
 
 TEST(IPv6AddressTest, Size) {
-    EXPECT_EQ(16, IPv6Address("dead:beef::1").size());
-    EXPECT_EQ(16, IPv6Address().size());
+    EXPECT_EQ(16UL, IPv6Address("dead:beef::1").size());
+    EXPECT_EQ(16UL, IPv6Address().size());
 }
 
 #if TINS_IS_CXX11
diff --git a/tests/src/ipv6_test.cpp b/tests/src/ipv6_test.cpp
index 021bfdf..029a161 100644
--- a/tests/src/ipv6_test.cpp
+++ b/tests/src/ipv6_test.cpp
@@ -336,7 +336,7 @@ TEST_F(IPv6Test, OptionIteration) {
     IPv6& ipv6 = pkt.rfind_pdu<IPv6>();
     const IPv6::headers_type& headers = ipv6.headers();
 
-    ASSERT_EQ(1, headers.size());
+    ASSERT_EQ(1UL, headers.size());
     const IPv6::ext_header& header = headers[0];
     EXPECT_EQ(IPv6::ROUTING, header.option());
 }
@@ -349,7 +349,7 @@ TEST_F(IPv6Test, OptionAddition) {
 
     const IPv6::headers_type& headers = ipv6.headers();
 
-    ASSERT_EQ(2, headers.size());
+    ASSERT_EQ(2UL, headers.size());
     EXPECT_EQ(IPv6::ROUTING, headers[0].option());
     EXPECT_EQ(IPv6::AUTHENTICATION, headers[1].option());
 
diff --git a/tests/src/pdu_iterator_test.cpp b/tests/src/pdu_iterator_test.cpp
index fda5ae0..3bb24ca 100644
--- a/tests/src/pdu_iterator_test.cpp
+++ b/tests/src/pdu_iterator_test.cpp
@@ -42,7 +42,7 @@ public:
 
         const PDU& pdu = *iterate_pdus(ip).begin();
         EXPECT_EQ(PDU::IP, pdu.pdu_type());
-        EXPECT_GT(const_cast<PDU&>(pdu).serialize().size(), 0);
+        EXPECT_GT(const_cast<PDU&>(pdu).serialize().size(), 0UL);
     }
 };