diff --git a/src/common/proxy_wasm/ngx_proxy_wasm_host.c b/src/common/proxy_wasm/ngx_proxy_wasm_host.c
index 331eec334..11eb5d80d 100644
--- a/src/common/proxy_wasm/ngx_proxy_wasm_host.c
+++ b/src/common/proxy_wasm/ngx_proxy_wasm_host.c
@@ -1702,14 +1702,14 @@ ngx_proxy_wasm_hfuncs_get_metric(ngx_wavm_instance_t *instance,
 
     ngx_memzero(trapmsg, NGX_MAX_ERROR_STR);
     p = ngx_sprintf(trapmsg,
-                    "could not retrieve metric id \"%ui\": ",
+                    "could not retrieve metric id \"%ui\"",
                     metric_id);
 
     if (rc == NGX_DECLINED) {
-        ngx_sprintf(p, "metric not found");
+        ngx_sprintf(p, ": metric not found");
 
     } else if (m->type == NGX_WA_METRIC_HISTOGRAM) {
-        ngx_sprintf(p, "metric is a histogram");
+        ngx_sprintf(p, ": metric is a histogram");
     }
 
     return ngx_proxy_wasm_result_trap(pwexec, (char *) trapmsg,