diff --git a/gcovr.cfg b/gcovr.cfg
index 4e242a4..3920172 100644
--- a/gcovr.cfg
+++ b/gcovr.cfg
@@ -1,4 +1,5 @@
 exclude-throw-branches = yes
+exclude-unreachable-branches = yes
 filter = include/mav
 exclude = include/mav/rapidxml/*
 exclude = include/mav/picosha2/*
\ No newline at end of file
diff --git a/include/mav/MessageSet.h b/include/mav/MessageSet.h
index ff34ebf..72757db 100644
--- a/include/mav/MessageSet.h
+++ b/include/mav/MessageSet.h
@@ -130,7 +130,7 @@ namespace mav {
         }
 
 
-        static bool _isPrefix(std::string_view prefix, std::string_view full) {
+        static bool _isPrefix(std::string_view prefix, std::string_view full) noexcept {
             return prefix == full.substr(0, prefix.size());
         }
 
diff --git a/tests/MessageSet.cpp b/tests/MessageSet.cpp
index 6a1874b..48e89ad 100644
--- a/tests/MessageSet.cpp
+++ b/tests/MessageSet.cpp
@@ -194,7 +194,7 @@ TEST_CASE("Enum value encoding") {
         CHECK_THROWS_AS(message_set.addFromXMLString(empty_value), mav::ParseError);
     }
 
-    SUBCASE("Enum with invalid value") {
+    SUBCASE("Enum with invalid value 1") {
         std::string invalid_value = R""""(
 <mavlink>
     <enums>
@@ -209,6 +209,35 @@ TEST_CASE("Enum value encoding") {
         CHECK_THROWS_AS(message_set.addFromXMLString(invalid_value), mav::ParseError);
     }
 
+    SUBCASE("Enum with invalid value 2") {
+        std::string invalid_value = R""""(
+<mavlink>
+    <enums>
+        <enum name="MY_ENUM_INVALID_VALUE">
+            <entry value="thisiswrong" name="INVALID" />
+        </enum>
+    </enums>
+</mavlink>
+)"""";
+
+        MessageSet message_set;
+        CHECK_THROWS_AS(message_set.addFromXMLString(invalid_value), mav::ParseError);
+    }
+
+    SUBCASE("Enum with invalid value 3") {
+        std::string invalid_value = R""""(
+<mavlink>
+    <enums>
+        <enum name="MY_ENUM_INVALID_VALUE">
+            <entry value="128thereismorecontent" name="INVALID" />
+        </enum>
+    </enums>
+</mavlink>
+)"""";
+
+        MessageSet message_set;
+        CHECK_THROWS_AS(message_set.addFromXMLString(invalid_value), mav::ParseError);
+    }
 
     SUBCASE("Enum with overflow value") {
         std::string invalid_value = R""""(
@@ -225,8 +254,20 @@ TEST_CASE("Enum value encoding") {
         CHECK_THROWS_AS(message_set.addFromXMLString(invalid_value), mav::ParseError);
     }
 
+    SUBCASE("Enum with non-base-2 exponential value") {
+        std::string invalid_value = R""""(
+<mavlink>
+    <enums>
+        <enum name="MY_ENUM_INVALID_VALUE">
+            <entry value="3**3" name="INVALID" />
+        </enum>
+    </enums>
+</mavlink>
+)"""";
 
-
+        MessageSet message_set;
+        CHECK_THROWS_AS(message_set.addFromXMLString(invalid_value), mav::ParseError);
+    }
 
 }