diff --git a/ok2curl/src/main/java/com/moczul/ok2curl/CurlBuilder.java b/ok2curl/src/main/java/com/moczul/ok2curl/CurlBuilder.java
index 0cf3517..99fad85 100644
--- a/ok2curl/src/main/java/com/moczul/ok2curl/CurlBuilder.java
+++ b/ok2curl/src/main/java/com/moczul/ok2curl/CurlBuilder.java
@@ -96,7 +96,7 @@ public String build() {
             parts.add(headerPart);
         }
 
-        if (contentType != null && !headers.containsKey(CONTENT_TYPE)) {
+        if (contentType != null && !containsName(CONTENT_TYPE, headers)) {
             parts.add(String.format(FORMAT_HEADER, CONTENT_TYPE, contentType));
         }
 
@@ -108,4 +108,14 @@ public String build() {
 
         return join(" ", parts);
     }
+
+    private boolean containsName(String name, List<Header> headers) {
+        for (Header header : headers) {
+            if (header.name().equals(name)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
 }