diff --git a/Cartfile b/Cartfile
index 35f2876..6a34252 100644
--- a/Cartfile
+++ b/Cartfile
@@ -1 +1 @@
-github "postmates/PMJSON" ~> 3.0
+github "postmates/PMJSON" ~> 4.0
diff --git a/Cartfile.resolved b/Cartfile.resolved
index e59e9bf..17981ae 100644
--- a/Cartfile.resolved
+++ b/Cartfile.resolved
@@ -1,2 +1,2 @@
-github "postmates/PMJSON" "v3.1.1"
-github "robbiehanson/CocoaAsyncSocket" "ec6c373de9eb7606a229ab927d1cce432073cc26"
+github "postmates/PMJSON" "v4.0.0"
+github "robbiehanson/CocoaAsyncSocket" "b179ea4013e94e31e6e637955e520ea4fb9d1b13"
diff --git a/PMHTTP.podspec b/PMHTTP.podspec
index 1b26ab8..595d4f3 100644
--- a/PMHTTP.podspec
+++ b/PMHTTP.podspec
@@ -28,5 +28,5 @@ Pod::Spec.new do |s|
   s.library    = 'c++'
   s.module_map = "Sources/pmhttp.modulemap"
 
-  s.dependency "PMJSON", "~> 3.0"
+  s.dependency "PMJSON", ">= 3.0", "< 5.0"
 end
diff --git a/README.md b/README.md
index c74b40d..d97d44a 100644
--- a/README.md
+++ b/README.md
@@ -410,6 +410,10 @@ work by you shall be dual licensed as above, without any additional terms or con
 
 ## Version History
 
+#### Development
+
+* Support PMJSON 4.x in addition to PMJSON 3.x with CocoaPods. Carthage doesn't support that kind of version range so it's now just set to PMJSON 4.x only.
+
 #### v4.4.2 (2019-08-13)
 
 * Fix a bug with the deprecated `HTTPManagerObjectParseRequest.credential` property where assigning to the property wouldn't work.