diff --git a/src/eap_peer/eap_teap.c b/src/eap_peer/eap_teap.c
index bc7f6f4f5..85b089ad4 100644
--- a/src/eap_peer/eap_teap.c
+++ b/src/eap_peer/eap_teap.c
@@ -319,6 +319,13 @@ static int eap_teap_init_phase2_method(struct eap_sm *sm,
 	if (!data->phase2_method)
 		return -1;
 
+	/* While RFC 7170 does not describe this, EAP-TEAP has been deployed
+	 * with implementations that use the EAP-FAST-MSCHAPv2, instead of the
+	 * EAP-MSCHAPv2, way of deriving the MSK for IMSK. Use that design here
+	 * to interoperate.
+	 */
+	sm->eap_fast_mschapv2 = true;
+
 	sm->init_phase2 = 1;
 	data->phase2_priv = data->phase2_method->init(sm);
 	sm->init_phase2 = 0;
diff --git a/src/eap_server/eap_server_teap.c b/src/eap_server/eap_server_teap.c
index 691b44a8d..1e5e9a562 100644
--- a/src/eap_server/eap_server_teap.c
+++ b/src/eap_server/eap_server_teap.c
@@ -1008,6 +1008,13 @@ static int eap_teap_phase2_init(struct eap_sm *sm, struct eap_teap_data *data,
 	if (!data->phase2_method)
 		return -1;
 
+	/* While RFC 7170 does not describe this, EAP-TEAP has been deployed
+	 * with implementations that use the EAP-FAST-MSCHAPv2, instead of the
+	 * EAP-MSCHAPv2, way of deriving the MSK for IMSK. Use that design here
+	 * to interoperate.
+	 */
+	sm->eap_fast_mschapv2 = true;
+
 	sm->init_phase2 = 1;
 	data->phase2_priv = data->phase2_method->init(sm);
 	sm->init_phase2 = 0;