diff --git a/agent/http.go b/agent/http.go
index 68abc426f0..1feab52d48 100644
--- a/agent/http.go
+++ b/agent/http.go
@@ -45,6 +45,11 @@ import (
 	"github.com/hashicorp/consul/proto/private/pbcommon"
 )
 
+const (
+	contentTypeHeader = "Content-Type"
+	plainContentType  = "text/plain; charset=utf-8"
+)
+
 var HTTPSummaries = []prometheus.SummaryDefinition{
 	{
 		Name: []string{"api", "http"},
@@ -222,7 +227,7 @@ func (s *HTTPHandlers) handler() http.Handler {
 			// If enableDebug register wrapped pprof handlers
 			if !s.agent.enableDebug.Load() && s.checkACLDisabled() {
 				resp.WriteHeader(http.StatusNotFound)
-				resp.Header().Set(api.ContentTypeHeader, api.PlainContentType)
+				resp.Header().Set(contentTypeHeader, plainContentType)
 				return
 			}
 
@@ -231,7 +236,7 @@ func (s *HTTPHandlers) handler() http.Handler {
 
 			authz, err := s.agent.delegate.ResolveTokenAndDefaultMeta(token, nil, nil)
 			if err != nil {
-				resp.Header().Set(api.ContentTypeHeader, api.PlainContentType)
+				resp.Header().Set(contentTypeHeader, plainContentType)
 				resp.WriteHeader(http.StatusForbidden)
 				return
 			}
@@ -241,7 +246,7 @@ func (s *HTTPHandlers) handler() http.Handler {
 			// TODO(partitions): should this be possible in a partition?
 			// TODO(acl-error-enhancements): We should return error details somehow here.
 			if authz.OperatorRead(nil) != acl.Allow {
-				resp.Header().Set(api.ContentTypeHeader, api.PlainContentType)
+				resp.Header().Set(contentTypeHeader, plainContentType)
 				resp.WriteHeader(http.StatusForbidden)
 				return
 			}
@@ -349,22 +354,22 @@ func ensureContentTypeHeader(next http.Handler, logger hclog.Logger) http.Handle
 	return http.HandlerFunc(func(resp http.ResponseWriter, req *http.Request) {
 		next.ServeHTTP(resp, req)
 
-		contentType := api.DetermineContentType(req)
+		contentType := api.SetContentType(req)
 
 		// validate request content-type header
-		reqContentType := req.Header.Get(api.ContentTypeHeader)
+		reqContentType := req.Header.Get(contentTypeHeader)
 		if reqContentType == "" || reqContentType != contentType {
 			logger.Debug("warning: request content-type is not supported", "request-path", req.URL)
 			// set request type to expected content-type
-			req.Header.Set(api.ContentTypeHeader, contentType)
+			req.Header.Set(contentTypeHeader, contentType)
 		}
 
 		// validate response content-type header
 		if resp != nil {
-			respContentType := resp.Header().Get(api.ContentTypeHeader)
+			respContentType := resp.Header().Get(contentTypeHeader)
 			if respContentType == "" || respContentType != contentType {
 				logger.Debug("warning: response content-type header not explicitly set.", "request-path", req.URL)
-				resp.Header().Set(api.ContentTypeHeader, contentType)
+				resp.Header().Set(contentTypeHeader, contentType)
 			}
 		}
 	})
@@ -414,7 +419,7 @@ func (s *HTTPHandlers) wrap(handler endpoint, methods []string) http.HandlerFunc
 				"error", err,
 			)
 			//set response type to plain to prevent XSS
-			resp.Header().Set(api.ContentTypeHeader, api.PlainContentType)
+			resp.Header().Set(contentTypeHeader, plainContentType)
 			resp.WriteHeader(http.StatusInternalServerError)
 			return
 		}
@@ -442,7 +447,7 @@ func (s *HTTPHandlers) wrap(handler endpoint, methods []string) http.HandlerFunc
 				"error", errMsg,
 			)
 			//set response type to plain to prevent XSS
-			resp.Header().Set(api.ContentTypeHeader, api.PlainContentType)
+			resp.Header().Set(contentTypeHeader, plainContentType)
 			resp.WriteHeader(http.StatusForbidden)
 			fmt.Fprint(resp, errMsg)
 			return
@@ -610,7 +615,7 @@ func (s *HTTPHandlers) wrap(handler endpoint, methods []string) http.HandlerFunc
 				obj, err = handler(resp, req)
 			}
 		}
-		contentType := api.JSONContentType
+		contentType := "application/json"
 		httpCode := http.StatusOK
 		if err != nil {
 			if errPayload, ok := err.(CodeWithPayloadError); ok {
@@ -623,7 +628,7 @@ func (s *HTTPHandlers) wrap(handler endpoint, methods []string) http.HandlerFunc
 				}
 			} else {
 				//set response type to plain to prevent XSS
-				resp.Header().Set(api.ContentTypeHeader, api.PlainContentType)
+				resp.Header().Set(contentTypeHeader, plainContentType)
 				handleErr(err)
 				return
 			}
@@ -632,11 +637,11 @@ func (s *HTTPHandlers) wrap(handler endpoint, methods []string) http.HandlerFunc
 			return
 		}
 		var buf []byte
-		if contentType == api.JSONContentType {
+		if contentType == "application/json" {
 			buf, err = s.marshalJSON(req, obj)
 			if err != nil {
 				//set response type to plain to prevent XSS
-				resp.Header().Set(api.ContentTypeHeader, api.PlainContentType)
+				resp.Header().Set(contentTypeHeader, plainContentType)
 				handleErr(err)
 				return
 			}
@@ -647,7 +652,7 @@ func (s *HTTPHandlers) wrap(handler endpoint, methods []string) http.HandlerFunc
 				}
 			}
 		}
-		resp.Header().Set(api.ContentTypeHeader, contentType)
+		resp.Header().Set(contentTypeHeader, contentType)
 		resp.WriteHeader(httpCode)
 		resp.Write(buf)
 	}
diff --git a/agent/http_test.go b/agent/http_test.go
index b5edf33667..377f913004 100644
--- a/agent/http_test.go
+++ b/agent/http_test.go
@@ -638,11 +638,11 @@ func TestHTTPAPIResponseHeaders(t *testing.T) {
 	`)
 	defer a.Shutdown()
 
-	requireHasHeadersSet(t, a, http.MethodGet, "/v1/agent/self", nil, api.JSONContentType)
+	requireHasHeadersSet(t, a, http.MethodGet, "/v1/agent/self", nil, "application/json")
 
 	// Check the Index page that just renders a simple message with UI disabled
 	// also gets the right headers.
-	requireHasHeadersSet(t, a, http.MethodGet, "/", nil, api.PlainContentType)
+	requireHasHeadersSet(t, a, http.MethodGet, "/", nil, "text/plain; charset=utf-8")
 }
 
 func TestHTTPAPISnapshotEndpointResponseHeaders(t *testing.T) {
@@ -684,8 +684,6 @@ func requireHasHeadersSet(t *testing.T, a *TestAgent, method, path string, body
 	hdrs := resp.Header()
 	reqHdrs := req.Header
 
-	fmt.Println("Body: ", resp.Body.String())
-
 	require.Equal(t, "*", hdrs.Get("Access-Control-Allow-Origin"),
 		"Access-Control-Allow-Origin header value incorrect")
 
@@ -719,7 +717,7 @@ func TestUIResponseHeaders(t *testing.T) {
 	defer a.Shutdown()
 
 	//response header for the UI appears to be being handled by the UI itself.
-	requireHasHeadersSet(t, a, http.MethodGet, "/ui", nil, api.PlainContentType)
+	requireHasHeadersSet(t, a, http.MethodGet, "/ui", nil, "text/plain; charset=utf-8")
 }
 
 func TestErrorContentTypeHeaderSet(t *testing.T) {
@@ -739,7 +737,7 @@ func TestErrorContentTypeHeaderSet(t *testing.T) {
 	`)
 	defer a.Shutdown()
 
-	requireHasHeadersSet(t, a, http.MethodGet, "/fake-path-doesn't-exist", nil, api.JSONContentType)
+	requireHasHeadersSet(t, a, http.MethodGet, "/fake-path-doesn't-exist", nil, "application/json")
 }
 
 func TestAcceptEncodingGzip(t *testing.T) {
diff --git a/api/api.go b/api/api.go
index 12009f3aed..91043b2b73 100644
--- a/api/api.go
+++ b/api/api.go
@@ -1088,21 +1088,23 @@ func (c *Client) doRequest(r *request) (time.Duration, *http.Response, error) {
 		return 0, nil, err
 	}
 
-	contentType := DetermineContentType(req)
+	contentType := SetContentType(req)
 
-	// validate request content-type header
-	reqContentType := req.Header.Get(ContentTypeHeader)
+	reqContentType := req.Header.Get(contentTypeHeader)
 	if reqContentType == "" || reqContentType != contentType {
-		req.Header.Set(ContentTypeHeader, contentType)
+		// Content-Type must always be set
+		req.Header.Set(contentTypeHeader, contentType)
 	}
 
 	start := time.Now()
 	resp, err := c.config.HttpClient.Do(req)
+
 	// validate response content-type header
 	if resp != nil {
-		respContentType := resp.Header.Get(ContentTypeHeader)
+		respContentType := resp.Header.Get(contentTypeHeader)
 		if respContentType == "" || respContentType != contentType {
-			resp.Header.Set(ContentTypeHeader, contentType)
+			// Content-Type must always be set
+			resp.Header.Set(contentTypeHeader, contentType)
 		}
 	}
 
diff --git a/api/content_type.go b/api/content_type.go
index 6bdb5c1a57..e749850807 100644
--- a/api/content_type.go
+++ b/api/content_type.go
@@ -9,9 +9,9 @@ import (
 )
 
 const (
-	ContentTypeHeader = "Content-Type"
-	PlainContentType  = "text/plain; charset=utf-8"
-	JSONContentType   = "application/json" // Default content type
+	contentTypeHeader = "Content-Type"
+	plainContentType  = "text/plain; charset=utf-8"
+	jsonContentType   = "application/json" // Default content type
 )
 
 // ContentTypeRule defines a rule for content type determination
@@ -55,23 +55,23 @@ var contentTypeRules = []contentTypeRule{
 	{
 		path:        "/ui",
 		method:      http.MethodGet,
-		contentType: PlainContentType,
+		contentType: plainContentType,
 	},
 }
 
-// DetermineContentType returns the appropriate content type based on the request
-// If the request is nil, returns the default content type
-func DetermineContentType(req *http.Request) string {
+// SetContentType sets the request and response Content-Type header
+func SetContentType(req *http.Request) string {
+	// If the request is nil, returns the default content type
 	if req == nil {
-		return PlainContentType
+		return plainContentType
 	}
 
 	if isIndexPage(req) {
-		return PlainContentType
+		return plainContentType
 	}
 
 	if strings.HasPrefix(req.URL.Path, "/v1/internal") {
-		return req.Header.Get(ContentTypeHeader)
+		return req.Header.Get(contentTypeHeader)
 	}
 
 	// Check against defined endpoint and required content type rules
@@ -82,7 +82,7 @@ func DetermineContentType(req *http.Request) string {
 	}
 
 	// Default to JSON for all other endpoints
-	return JSONContentType
+	return jsonContentType
 }
 
 // matchesRule checks if a request matches a content type rule