diff --git a/srv/.lua/jwt.lua b/srv/.lua/jwt.lua
index c7adcc0..6d1f317 100644
--- a/srv/.lua/jwt.lua
+++ b/srv/.lua/jwt.lua
@@ -253,6 +253,17 @@ function JWS.VerifyTable(jwtTable, key, algorithms)
     assert(type(jwtTable.header) == "table", "Parameter: 'jwtTable' does not contain a header table")
     assert(jwtTable.payload ~= nil, "Parameter: 'jwtTable' does not contain a payload")
 
+    -- Claims (optional)
+    if(jwtTable.payload.nbf ~= nil) then
+        assert(type(jwtTable.payload.nbf) == "number", "Claim: 'nfb' must be a number")
+        assert(jwtTable.payload.nbf <= GetDate(), "Claim: 'nfb' is not valid")
+    end
+
+    if(jwtTable.payload.exp ~= nil) then
+        assert(type(jwtTable.payload.exp) == "number", "Claim: 'exp' must be a number")
+        assert(jwtTable.payload.exp >= GetDate(), "Claim: 'exp' must not be expired")
+    end
+
     -- if no algorithms are specified, fall back onto the supported algorithms
     algorithms = algorithms or JWA.supported
     if type(algorithms) == "string" then algorithms = { algorithms } end
@@ -435,4 +446,4 @@ JWT._Common = Common
 JWT._JWS = JWS
 JWT._JWA = JWA
 
-return JWT
\ No newline at end of file
+return JWT