diff --git a/lix/libexpr/eval-cache.hh b/lix/libexpr/eval-cache.hh
index bd8541b49..5135b0fac 100644
--- a/lix/libexpr/eval-cache.hh
+++ b/lix/libexpr/eval-cache.hh
@@ -53,7 +53,7 @@ public:
     ref<AttrCursor> getRoot();
 };
 
-enum AttrType {
+enum AttrType : uint8_t {
     Placeholder = 0,
     FullAttrs = 1,
     String = 2,
diff --git a/lix/libexpr/value.hh b/lix/libexpr/value.hh
index bf20f2c5f..0e92e08d5 100644
--- a/lix/libexpr/value.hh
+++ b/lix/libexpr/value.hh
@@ -284,6 +284,7 @@ private:
 
     InternalType internalType() const
     {
+        // NOLINTNEXTLINE(lix-cast-to-non-fixed-enum): TAG_MASK ensures it's in range
         return InternalType(raw & TAG_MASK);
     }
 
@@ -723,6 +724,8 @@ public:
 
         Type type() const
         {
+            // TAG_MASK == 7, max enumerator is 5, so all possible values are in range
+            // NOLINTNEXTLINE(lix-cast-to-non-fixed-enum)
             return Type(raw & TAG_MASK);
         }
     };
diff --git a/lix/libutil/logging.hh b/lix/libutil/logging.hh
index 0e4a0ae9b..a1103a29c 100644
--- a/lix/libutil/logging.hh
+++ b/lix/libutil/logging.hh
@@ -12,7 +12,7 @@
 
 namespace nix {
 
-typedef enum {
+enum ActivityType : uint8_t {
     actUnknown = 0,
     actCopyPath = 100,
     actFileTransfer = 101,
@@ -47,12 +47,12 @@ typedef enum {
      */
     actPostBuildHook = 110,
     actBuildWaiting = 111,
-} ActivityType;
+};
 
 template<>
 struct json::is_integral_enum<ActivityType> : std::true_type {};
 
-typedef enum {
+enum ResultType : uint8_t {
     /** Fields:
      * 0: int: bytes linked
      */
@@ -88,7 +88,7 @@ typedef enum {
      * 0: string: last line
      */
     resPostBuildLogLine = 107,
-} ResultType;
+};
 
 template<>
 struct json::is_integral_enum<ResultType> : std::true_type {};