diff --git a/acquirer/api.go b/acquirer/api.go
index 7a4bfbc..71b5c7b 100644
--- a/acquirer/api.go
+++ b/acquirer/api.go
@@ -46,6 +46,7 @@ func (a *API) createMerchant(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(http.StatusCreated)
 	json.NewEncoder(w).Encode(account)
 }
@@ -67,6 +68,7 @@ func (a *API) createPayment(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(http.StatusCreated)
 	json.NewEncoder(w).Encode(payment)
 }
@@ -85,6 +87,7 @@ func (a *API) getPayment(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(http.StatusOK)
 	json.NewEncoder(w).Encode(payment)
 }
diff --git a/issuer/api.go b/issuer/api.go
index e795e69..241fdca 100644
--- a/issuer/api.go
+++ b/issuer/api.go
@@ -45,6 +45,7 @@ func (a *API) createAccount(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(http.StatusCreated)
 	json.NewEncoder(w).Encode(account)
 }
@@ -62,6 +63,7 @@ func (a *API) getAccount(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(http.StatusOK)
 	json.NewEncoder(w).Encode(account)
 }
@@ -75,6 +77,7 @@ func (a *API) issueCard(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(http.StatusCreated)
 	json.NewEncoder(w).Encode(card)
 }
@@ -88,6 +91,7 @@ func (a *API) getTransactions(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(http.StatusOK)
 	json.NewEncoder(w).Encode(transactions)
 }