diff --git a/openssl_alloc.cpp b/openssl_alloc.cpp
new file mode 100644
index 0000000..ddf278c
--- /dev/null
+++ b/openssl_alloc.cpp
@@ -0,0 +1,29 @@
+#include "openssl_alloc.hpp"
+
+#if OPENSSL_VERSION_NUMBER < 0x10100000L
+
+#include <string.h>
+
+static void* OPENSSL_zalloc(size_t num)
+{
+    void* ret = OPENSSL_malloc(num);
+
+    if (ret != NULL)
+    {
+        memset(ret, 0, num);
+    }
+    return ret;
+}
+
+EVP_MD_CTX* EVP_MD_CTX_new(void)
+{
+    return (EVP_MD_CTX*)OPENSSL_zalloc(sizeof(EVP_MD_CTX));
+}
+
+void EVP_MD_CTX_free(EVP_MD_CTX* ctx)
+{
+    EVP_MD_CTX_cleanup(ctx);
+    OPENSSL_free(ctx);
+}
+
+#endif