diff --git a/openbsc/src/libcommon/gsup_client.c b/openbsc/src/libcommon/gsup_client.c
index 0360e0a..4c1fe61 100644
--- a/openbsc/src/libcommon/gsup_client.c
+++ b/openbsc/src/libcommon/gsup_client.c
@@ -155,6 +155,7 @@
 	int rc;
 	struct msgb *msg_tx;
 
+	/* If the oap_state is disabled, this will reject the messages. */
 	rc = oap_client_handle(&gsupc->oap_state, msg_rx, &msg_tx);
 	msgb_free(msg_rx);
 	if (rc < 0)
diff --git a/openbsc/src/libcommon/oap_client.c b/openbsc/src/libcommon/oap_client.c
index 46dbcdd..e372ede 100644
--- a/openbsc/src/libcommon/oap_client.c
+++ b/openbsc/src/libcommon/oap_client.c
@@ -21,6 +21,7 @@
  */
 
 #include <string.h>
+#include <errno.h>
 
 #include <osmocom/core/utils.h>
 #include <osmocom/crypt/auth.h>
@@ -224,6 +225,21 @@
 		return -10;
 	}
 
+	switch (state->state) {
+	case OAP_UNINITIALIZED:
+		LOGP(DLOAP, LOGL_ERROR,
+		     "Received OAP message %d, but the OAP client is"
+		     " not initialized\n", oap_msg.message_type);
+		return -ENOTCONN;
+	case OAP_DISABLED:
+		LOGP(DLOAP, LOGL_ERROR,
+		     "Received OAP message %d, but the OAP client is"
+		     " disabled\n", oap_msg.message_type);
+		return -ENOTCONN;
+	default:
+		break;
+	}
+
 	switch (oap_msg.message_type) {
 	case OAP_MSGT_CHALLENGE_REQUEST:
 		return handle_challenge(state, &oap_msg, msg_tx);