diff --git a/src/core/symcache.c b/src/core/symcache.c
index 4c30238c..01a9a9b5 100644
--- a/src/core/symcache.c
+++ b/src/core/symcache.c
@@ -43,7 +43,8 @@ void janet_symcache_init() {
     if (NULL == janet_vm.cache) {
         JANET_OUT_OF_MEMORY;
     }
-    memset(&janet_vm.gensym_counter, 0, sizeof(janet_vm.gensym_counter));
+    memset(&janet_vm.gensym_counter, '0', sizeof(janet_vm.gensym_counter));
+    janet_vm.gensym_counter[0] = '_';
     janet_vm.cache_count = 0;
     janet_vm.cache_deleted = 0;
 }
diff --git a/test/suite0007.janet b/test/suite0007.janet
index 62392e63..f24aa1a1 100644
--- a/test/suite0007.janet
+++ b/test/suite0007.janet
@@ -311,4 +311,6 @@
 (tracev (def my-unique-var-name true))
 (assert my-unique-var-name "tracev upscopes")
 
+(assert (pos? (length (gensym))) "gensym not empty, regression #753")
+
 (end-suite)