diff --git a/src/lib/exercises/src/hackerrank/warmup/time_conversion.cpp b/src/lib/exercises/src/hackerrank/warmup/time_conversion.cpp
index a9f74c4..5b45835 100644
--- a/src/lib/exercises/src/hackerrank/warmup/time_conversion.cpp
+++ b/src/lib/exercises/src/hackerrank/warmup/time_conversion.cpp
@@ -41,6 +41,10 @@ std::string timeConversion(const std::string &s) {
   int hour;
   hour_str >> hour;
 
+  if (hour < 0 || hour > 23) {
+    throw std::invalid_argument("Invalid hour value");
+  }
+
   if (hour >= 12) {
     hour = 0;
   }
diff --git a/src/tests/unit/lib/hackerrank/warmup/test_conversion.test.cpp b/src/tests/unit/lib/hackerrank/warmup/test_conversion.test.cpp
index d29460f..1c74b3a 100644
--- a/src/tests/unit/lib/hackerrank/warmup/test_conversion.test.cpp
+++ b/src/tests/unit/lib/hackerrank/warmup/test_conversion.test.cpp
@@ -36,3 +36,8 @@ TEST_CASE("time_conversion helper functions edge cases",
   CHECK(hackerrank::warmup::firstN("", 0) == "");
   CHECK(hackerrank::warmup::lastN("", 0) == "");
 }
+
+TEST_CASE("time_conversion invalid input", "[hackerrank] [invalid] [warmup]") {
+  CHECK_THROWS_AS(hackerrank::warmup::timeConversion("25:01:00AM"),
+                  std::invalid_argument);
+}