diff --git a/lib/hooks/hooks-internal.c b/lib/hooks/hooks-internal.c
index 070e68359..d10efb92e 100644
--- a/lib/hooks/hooks-internal.c
+++ b/lib/hooks/hooks-internal.c
@@ -16,6 +16,9 @@ REGISTER_HOOK("fix_ts", "Update timestamps of sample if not set", 0, 0, hook_fix
 int hook_fix_ts(struct hook *h, int when, struct hook_info *j)
 {
 	struct timespec now = time_now();
+
+	if (when != HOOK_READ)
+		return 0;
 	
 	assert(j->smps);
 
@@ -41,6 +44,9 @@ int hook_fix_ts(struct hook *h, int when, struct hook_info *j)
 REGISTER_HOOK("restart", "Call restart hooks for current path", 1, 1, hook_restart, HOOK_INTERNAL | HOOK_READ)
 int hook_restart(struct hook *h, int when, struct hook_info *j)
 {
+	if (when != HOOK_READ)
+		return 0;
+	
 	assert(j->smps);
 	assert(j->path);
 
@@ -68,6 +74,9 @@ int hook_drop(struct hook *h, int when, struct hook_info *j)
 {
 	int i, ok, dist;
 	
+	if (when != HOOK_READ)
+		return 0;
+	
 	assert(j->smps);
 
 	for (i = 0, ok = 0; i < j->cnt; i++) {