--- a/js/src/vm/SPSProfiler.cpp
+++ b/js/src/vm/SPSProfiler.cpp
@@ -345,18 +345,20 @@ SPSProfiler::allocProfileString(JSScript
     char* cstr = js_pod_malloc<char>(len + 1);
     if (cstr == nullptr)
         return nullptr;
 
     // Construct the descriptive string.
     DebugOnly<size_t> ret;
     if (atom) {
         UniqueChars atomStr = StringToNewUTF8CharsZ(nullptr, *atom);
-        if (!atomStr)
+        if (!atomStr) {
+            js_free(cstr);
             return nullptr;
+        }
         ret = JS_snprintf(cstr, len + 1, "%s (%s:%" PRIu64 ")", atomStr.get(), filename, lineno);
     } else {
         ret = JS_snprintf(cstr, len + 1, "%s:%" PRIu64, filename, lineno);
     }
 
     MOZ_ASSERT(ret == len, "Computed length should match actual length!");
 
     return cstr;