diff --git a/crypto/engine/hw_aep.c b/crypto/engine/hw_aep.c
index 8b8380a58..5f1772ea9 100644
--- a/crypto/engine/hw_aep.c
+++ b/crypto/engine/hw_aep.c
@@ -474,6 +474,7 @@ static int aep_init(ENGINE *e)
 
 	if(aep_dso)
 		DSO_free(aep_dso);
+	aep_dso = NULL;
 		
 	p_AEP_OpenConnection    = NULL;
 	p_AEP_ModExp            = NULL;
diff --git a/crypto/engine/hw_atalla.c b/crypto/engine/hw_atalla.c
index e9eff9fad..2b8342bbd 100644
--- a/crypto/engine/hw_atalla.c
+++ b/crypto/engine/hw_atalla.c
@@ -375,6 +375,7 @@ static int atalla_init(ENGINE *e)
 err:
 	if(atalla_dso)
 		DSO_free(atalla_dso);
+	atalla_dso = NULL;
 	p_Atalla_GetHardwareConfig = NULL;
 	p_Atalla_RSAPrivateKeyOpFn = NULL;
 	p_Atalla_GetPerformanceStatistics = NULL;
diff --git a/crypto/engine/hw_ubsec.c b/crypto/engine/hw_ubsec.c
index 5234a08a0..8fb834af3 100644
--- a/crypto/engine/hw_ubsec.c
+++ b/crypto/engine/hw_ubsec.c
@@ -454,6 +454,7 @@ static int ubsec_init(ENGINE *e)
 err:
 	if(ubsec_dso)
 		DSO_free(ubsec_dso);
+	ubsec_dso = NULL;
 	p_UBSEC_ubsec_bytes_to_bits = NULL;
 	p_UBSEC_ubsec_bits_to_bytes = NULL;
 	p_UBSEC_ubsec_open = NULL;