diff --git a/library/ssl_cache.c b/library/ssl_cache.c
index d93508c..048c21d 100644
--- a/library/ssl_cache.c
+++ b/library/ssl_cache.c
@@ -92,8 +92,8 @@
     mbedtls_ssl_cache_entry *entry;
 
 #if defined(MBEDTLS_THREADING_C)
-    if (mbedtls_mutex_lock(&cache->mutex) != 0) {
-        return 1;
+    if ((ret = mbedtls_mutex_lock(&cache->mutex)) != 0) {
+        return ret;
     }
 #endif
 
@@ -114,7 +114,7 @@
 exit:
 #if defined(MBEDTLS_THREADING_C)
     if (mbedtls_mutex_unlock(&cache->mutex) != 0) {
-        ret = 1;
+        ret = MBEDTLS_ERR_THREADING_MUTEX_ERROR;
     }
 #endif
 
@@ -318,7 +318,7 @@
 exit:
 #if defined(MBEDTLS_THREADING_C)
     if (mbedtls_mutex_unlock(&cache->mutex) != 0) {
-        ret = 1;
+        ret = MBEDTLS_ERR_THREADING_MUTEX_ERROR;
     }
 #endif
 
@@ -341,8 +341,8 @@
     mbedtls_ssl_cache_entry *prev;
 
 #if defined(MBEDTLS_THREADING_C)
-    if (mbedtls_mutex_lock(&cache->mutex) != 0) {
-        return 1;
+    if ((ret = mbedtls_mutex_lock(&cache->mutex)) != 0) {
+        return ret;
     }
 #endif
 
@@ -373,7 +373,7 @@
 exit:
 #if defined(MBEDTLS_THREADING_C)
     if (mbedtls_mutex_unlock(&cache->mutex) != 0) {
-        ret = 1;
+        ret = MBEDTLS_ERR_THREADING_MUTEX_ERROR;
     }
 #endif