diff --git a/src/resolver.c b/src/resolver.c
index e8e6f49..c34fb91 100644
--- a/src/resolver.c
+++ b/src/resolver.c
@@ -565,7 +565,7 @@ static int resolver_ares_srv_lookup(xmpp_ctx_t *ctx,
 #include <winsock2.h>
 #include <ws2tcpip.h>
 #include <windns.h>
-#include <Iphlpapi.h>
+#include <iphlpapi.h>
 
 struct dnsquery_header {
     unsigned short id;
diff --git a/src/sock.c b/src/sock.c
index a7c82fa..5e98db5 100644
--- a/src/sock.c
+++ b/src/sock.c
@@ -21,8 +21,8 @@
 #ifdef _WIN32
 #include <winsock2.h>
 #include <ws2tcpip.h>
-#include <Iphlpapi.h>
-#include <Mstcpip.h> /* tcp_keepalive */
+#include <iphlpapi.h>
+#include <mstcpip.h> /* tcp_keepalive */
 #else
 #include <errno.h>
 #include <unistd.h>