diff --git a/src/lib/util/tests/io_utilities_unittest.cc b/src/lib/util/tests/io_utilities_unittest.cc
index 6ecbf18ab1..9573d2da4e 100644
--- a/src/lib/util/tests/io_utilities_unittest.cc
+++ b/src/lib/util/tests/io_utilities_unittest.cc
@@ -42,7 +42,7 @@ TEST(asioutil, readUint16) {
 }
 
 TEST(asioutil, readUint16OutOfRange) {
-    uint8_t data;
+    uint8_t data = 0;
     EXPECT_THROW(readUint16(&data, sizeof(data)), isc::OutOfRange);
 }
 
@@ -87,7 +87,7 @@ const static uint32_t test32[] = {
 };
 
 TEST(asioutil, readUint32) {
-    uint8_t data[8];
+    uint8_t data[8] = {0, 0, 0, 0, 0, 0, 0, 0};
 
     // make sure that we can read data, regardless of
     // the memory alignment. That' why we need to repeat
@@ -103,7 +103,7 @@ TEST(asioutil, readUint32) {
 }
 
 TEST(asioutil, readUint32OutOfRange) {
-    uint8_t data[3];
+    uint8_t data[3] = {0, 0, 0};
     EXPECT_THROW(readUint32(data, sizeof(data)), isc::OutOfRange);
 }