diff --git a/plugins/in_opentelemetry/opentelemetry_prot.c b/plugins/in_opentelemetry/opentelemetry_prot.c
index 0de3c3b1221..f6b6f3396d2 100644
--- a/plugins/in_opentelemetry/opentelemetry_prot.c
+++ b/plugins/in_opentelemetry/opentelemetry_prot.c
@@ -2175,6 +2175,12 @@ static int process_payload_metrics_ng(struct flb_opentelemetry *ctx,
 
     offset = 0;
 
+    if (request->content_type == NULL) {
+        flb_error("[otel] content type missing");
+
+        return -1;
+    }
+
     if (strcasecmp(request->content_type, "application/grpc") == 0) {
         if (cfl_sds_len(request->body) < 5) {
             return -1;
@@ -2185,12 +2191,18 @@ static int process_payload_metrics_ng(struct flb_opentelemetry *ctx,
                                                  cfl_sds_len(request->body) - 5,
                                                  &offset);
     }
-    else {
+    else if (strcasecmp(request->content_type, "application/x-protobuf") == 0 ||
+             strcasecmp(request->content_type, "application/json") == 0) {
         result = cmt_decode_opentelemetry_create(&decoded_contexts,
                                                 request->body,
                                                 cfl_sds_len(request->body),
                                                 &offset);
     }
+    else {
+        flb_plg_error(ctx->ins, "Unsupported content type %s", request->content_type);
+
+        return -1;
+    }
 
     if (result == CMT_DECODE_OPENTELEMETRY_SUCCESS) {
         cfl_list_foreach(iterator, &decoded_contexts) {
@@ -2221,6 +2233,12 @@ static int process_payload_traces_proto_ng(struct flb_opentelemetry *ctx,
 
     offset = 0;
 
+    if (request->content_type == NULL) {
+        flb_error("[otel] content type missing");
+
+        return -1;
+    }
+
     if (strcasecmp(request->content_type, "application/grpc") == 0) {
         if (cfl_sds_len(request->body) < 5) {
             return -1;
@@ -2231,12 +2249,18 @@ static int process_payload_traces_proto_ng(struct flb_opentelemetry *ctx,
                                                  cfl_sds_len(request->body) - 5,
                                                  &offset);
     }
-    else {
+    else if (strcasecmp(request->content_type, "application/x-protobuf") == 0 ||
+             strcasecmp(request->content_type, "application/json") == 0) {
         result = ctr_decode_opentelemetry_create(&decoded_context,
                                                 request->body,
                                                 cfl_sds_len(request->body),
                                                 &offset);
     }
+    else {
+        flb_plg_error(ctx->ins, "Unsupported content type %s", request->content_type);
+
+        return -1;
+    }
 
     if (result == 0) {
         result = flb_input_trace_append(ctx->ins, NULL, 0, decoded_context);