diff --git a/external/sha1/sha1.h b/external/sha1/sha1.h
index 7354d13..93d717a 100644
--- a/external/sha1/sha1.h
+++ b/external/sha1/sha1.h
@@ -45,6 +45,13 @@ extern "C" {
 #include <stdlib.h>
 #include "../../src/stdint.hpp"
 
+/* Avoid collision with libssh et al. */
+#define sha1_ctxt   zmq_sha1_ctxt
+#define sha1_init   zmq_sha1_init
+#define sha1_pad    zmq_sha1_pad
+#define sha1_loop   zmq_sha1_loop
+#define sha1_result zmq_sha1_result
+
 struct sha1_ctxt
 {
 	union