diff --git a/CHANGELOG.md b/CHANGELOG.md
index f8a5e14..0ff9c25 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added a launcher function `launch` to make it easier to launch the app.
 - Semantic caching enabled by SemanticCaches.jl. You can change it by setting `cached=false` in the `launch()` function.
 
+### Fixed 
+- Fixed a bug when caching would error for certain types of HTTP body (eg, `IOBuffer`)
+
+
 ## [0.3.0]
 
 ### Added
diff --git a/src/CacheLayer.jl b/src/CacheLayer.jl
index abbff43..7124619 100644
--- a/src/CacheLayer.jl
+++ b/src/CacheLayer.jl
@@ -32,7 +32,9 @@ const HASH_CACHE = HashCache()
 function cache_layer(handler)
     return function (req; kw...)
         VERBOSE = Base.get(ENV, "CACHES_VERBOSE", "true") == "true"
-        if req.method == "POST" && !isempty(req.body)
+        has_body = (req.body isa IOBuffer ||
+                    (req.body isa AbstractVector && !isempty(req.body)))
+        if req.method == "POST" && has_body
             body = JSON3.read(copy(req.body))
             ## chat/completions is for OpenAI, v1/messages is for Anthropic
             if occursin("v1/chat/completions", req.target) ||