diff --git a/plugins/in_collectd/netprot.c b/plugins/in_collectd/netprot.c
index a7f13e92d1f..dd2d11104a9 100644
--- a/plugins/in_collectd/netprot.c
+++ b/plugins/in_collectd/netprot.c
@@ -247,8 +247,9 @@ int netprot_to_msgpack(char *buf, int len, struct mk_list *tdb,
         part_type = be16read(buf);
         part_len = be16read((unsigned char *) buf + 2);
 
-        if (len < part_len) {
-            flb_error("[in_collectd] data truncated (%i < %i)", len, part_len);
+        if (part_len < 4 || len < part_len) {
+            flb_error("[in_collectd] invalid part length (%i, remaining %i)",
+                      part_len, len);
             return -1;
         }
 
@@ -268,7 +269,7 @@ int netprot_to_msgpack(char *buf, int len, struct mk_list *tdb,
 
         switch (part_type) {
             case PART_HOST:
-                if (ptr[size] == '\0') {
+                if (size > 0 && ptr[size - 1] == '\0') {
                     hdr.host = ptr;
                 }
                 break;
@@ -279,22 +280,22 @@ int netprot_to_msgpack(char *buf, int len, struct mk_list *tdb,
                 hdr.time = hr2time(be64read(ptr));
                 break;
             case PART_PLUGIN:
-                if (ptr[size] == '\0') {
+                if (size > 0 && ptr[size - 1] == '\0') {
                     hdr.plugin = ptr;
                 }
                 break;
             case PART_PLUGIN_INSTANCE:
-                if (ptr[size] == '\0') {
+                if (size > 0 && ptr[size - 1] == '\0') {
                     hdr.plugin_instance = ptr;
                 }
                 break;
             case PART_TYPE:
-                if (ptr[size] == '\0') {
+                if (size > 0 && ptr[size - 1] == '\0') {
                     hdr.type = ptr;
                 }
                 break;
             case PART_TYPE_INSTANCE:
-                if (ptr[size] == '\0') {
+                if (size > 0 && ptr[size - 1] == '\0') {
                     hdr.type_instance = ptr;
                 }
                 break;