diff --git a/src/lib/core/CASEAuthTag.h b/src/lib/core/CASEAuthTag.h
index cd490d70d28334..e673848a988dce 100644
--- a/src/lib/core/CASEAuthTag.h
+++ b/src/lib/core/CASEAuthTag.h
@@ -94,7 +94,7 @@ constexpr CASEAuthTag CASEAuthTagFromNodeId(NodeId aNodeId)
     return aNodeId & kMaskCASEAuthTag;
 }
 
-constexpr CASEAuthTag IsValidCASEAuthTag(CASEAuthTag aCAT)
+constexpr bool IsValidCASEAuthTag(CASEAuthTag aCAT)
 {
     return (aCAT & kTagVersionMask) > 0;
 }