diff --git a/libnm-core/nm-utils-private.h b/libnm-core/nm-utils-private.h
index 3219bb3772..a337a8ad07 100644
--- a/libnm-core/nm-utils-private.h
+++ b/libnm-core/nm-utils-private.h
@@ -21,6 +21,10 @@
 #ifndef __NM_UTILS_PRIVATE_H__
 #define __NM_UTILS_PRIVATE_H__
 
+#ifdef __NETWORKMANAGER_TYPES_H__
+#error "nm-utils-private.h" must not be used outside of libnm-core/. Do you want "nm-core-internal.h"?
+#endif
+
 #include "nm-setting-private.h"
 #include "nm-setting-ip-config.h"
 
diff --git a/src/nm-types.h b/src/nm-types.h
index 1c0ba9b46a..3fa587932e 100644
--- a/src/nm-types.h
+++ b/src/nm-types.h
@@ -21,6 +21,10 @@
 #ifndef __NETWORKMANAGER_TYPES_H__
 #define __NETWORKMANAGER_TYPES_H__
 
+#ifdef __NM_UTILS_PRIVATE_H__
+#error "nm-utils-private.h" must not be used outside of libnm-core/. Do you want "nm-core-internal.h"?
+#endif
+
 /* core */
 typedef struct _NMActiveConnection   NMActiveConnection;
 typedef struct _NMVpnConnection      NMVpnConnection;