diff --git a/include/villas/hook.hpp b/include/villas/hook.hpp
index 3a91eaf96..e8a88a72b 100644
--- a/include/villas/hook.hpp
+++ b/include/villas/hook.hpp
@@ -64,8 +64,8 @@ protected:
 	enum State state;
 
 	int flags;
-	int priority; /**< A priority to change the order of execution within one type of hook. */
-	int enabled;  /**< Is this hook active? */
+	unsigned priority;		/**< A priority to change the order of execution within one type of hook. */
+	bool enabled;			/**< Is this hook active? */
 
 	struct vpath *path;
 	struct vnode *node;
@@ -141,7 +141,7 @@ public:
 		return Reason::OK;
 	};
 
-	int getPriority() const
+	unsigned getPriority() const
 	{
 		return priority;
 	}
@@ -199,7 +199,7 @@ public:
 	virtual Hook * make(struct vpath *p, struct vnode *n) = 0;
 
 	virtual int getFlags() const = 0;
-	virtual int getPriority() const = 0;
+	virtual unsigned getPriority() const = 0;
 
 	virtual
 	std::string
@@ -207,7 +207,7 @@ public:
 	{ return "hook"; }
 };
 
-template <typename T, const char *name, const char *desc, int flags = 0, int prio = 99>
+template <typename T, const char *name, const char *desc, int flags = 0, unsigned prio = 99>
 class HookPlugin : public HookFactory {
 
 public:
@@ -234,7 +234,7 @@ public:
 	getFlags() const
 	{ return flags; }
 
-	virtual int
+	virtual unsigned
 	getPriority() const
 	{ return prio; }
 };
diff --git a/lib/hook.cpp b/lib/hook.cpp
index 86a82119d..16f02afc7 100644
--- a/lib/hook.cpp
+++ b/lib/hook.cpp
@@ -86,13 +86,22 @@ void Hook::parse(json_t *json)
 
 	assert(state != State::STARTED);
 
+	int prio;
+	int en;
+
 	ret = json_unpack_ex(json, &err, 0, "{ s?: i, s?: b }",
-		"priority", &priority,
-		"enabled", &enabled
+		"priority", &prio,
+		"enabled", &en
 	);
 	if (ret)
 		throw ConfigError(json, err, "node-config-hook");
 
+	if (prio < 0)
+		throw ConfigError(json, "node-config-hook", "Priority must be equal or larger than zero");
+
+	priority = prio;
+	enabled = en;
+
 	config = json;
 
 	state = State::PARSED;