diff --git a/src/OpenAI.jl b/src/OpenAI.jl
index c811be8..2a999c5 100644
--- a/src/OpenAI.jl
+++ b/src/OpenAI.jl
@@ -8,17 +8,7 @@ const BASE_URL_v1 = "https://api.openai.com/v1"
 function build_params(kwargs)
     isempty(kwargs) && return nothing
     buf = IOBuffer()
-    write(buf, '{')
-    for (i, (k, v)) in enumerate(kwargs)
-        write(buf, '"', k, '"', ':')
-        if isnothing(v)
-            write(buf, "null")
-        else
-            write(buf, repr(v))
-        end
-        i == length(kwargs) || write(buf, ',')
-    end
-    write(buf, '}')
+    JSON3.write(buf, kwargs)
     seekstart(buf)
     return buf
 end
diff --git a/test/completion.jl b/test/completion.jl
index e4a6eab..86a418b 100644
--- a/test/completion.jl
+++ b/test/completion.jl
@@ -6,10 +6,10 @@
   r = create_completion(
     ENV["OPENAI_API_KEY"], 
     r.response["data"][begin]["id"];
-    prompt = "Say this is a test"
+    prompt = "Say \"this is a test\""
   )
   println(r.response["choices"][begin]["text"])
   if !=(r.status, 200)
     @test false
   end
-end
\ No newline at end of file
+end