diff --git a/include/mbedtls/x509_crt.h b/include/mbedtls/x509_crt.h
index 3388c3b..2f652b7 100644
--- a/include/mbedtls/x509_crt.h
+++ b/include/mbedtls/x509_crt.h
@@ -183,7 +183,10 @@
     int parent_is_trusted; /* -1 if find_parent is not in progress */
 
     /* for verify_chain() */
-    mbedtls_x509_crt *child; /* non-null iff in progress */
+    enum {
+        x509_crt_rs_none,
+        x509_crt_rs_find_parent,
+    } in_progress;  /* none if no operation is in progress */
     int self_cnt;
     mbedtls_x509_crt_verify_chain ver_chain;
 
diff --git a/library/x509_crt.c b/library/x509_crt.c
index 69cec4d..586ec83 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -2250,14 +2250,15 @@
 
 #if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
     /* resume if we had an operation in progress */
-    if( rs_ctx != NULL && rs_ctx->child != NULL )
+    if( rs_ctx != NULL && rs_ctx->in_progress == x509_crt_rs_find_parent )
     {
         /* restore saved state */
-        child = rs_ctx->child;
-        self_cnt = rs_ctx->self_cnt;
         *ver_chain = rs_ctx->ver_chain; /* struct copy */
+        self_cnt = rs_ctx->self_cnt;
 
+        /* restore derived state */
         cur = &ver_chain->items[ver_chain->len - 1];
+        child = cur->crt;
         flags = &cur->flags;
 
         goto find_parent;
@@ -2314,7 +2315,7 @@
         if( rs_ctx != NULL && ret == MBEDTLS_ERR_ECP_IN_PROGRESS )
         {
             /* save state */
-            rs_ctx->child = child;
+            rs_ctx->in_progress = x509_crt_rs_find_parent;
             rs_ctx->self_cnt = self_cnt;
             rs_ctx->ver_chain = *ver_chain; /* struct copy */
 
@@ -2681,7 +2682,7 @@
 
     ctx->parent_is_trusted = -1;
 
-    ctx->child = NULL;
+    ctx->in_progress = x509_crt_rs_none;
     ctx->self_cnt = 0;
     x509_crt_verify_chain_reset( &ctx->ver_chain );
 }