Move variable declaration to the top its block for MSVC compatibility.
diff --git a/src/arena.c b/src/arena.c
index bf78995..1eb4000 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -2022,6 +2022,7 @@
 		 * following run, then merge the first part with the existing
 		 * allocation.
 		 */
+		arena_run_t *run;
 		size_t flag_dirty, splitsize, usize;
 
 		usize = s2u(size + extra);
@@ -2030,8 +2031,7 @@
 		assert(usize >= usize_min);
 		splitsize = usize - oldsize;
 
-		arena_run_t *run = &arena_miscelm_get(chunk,
-		    pageind+npages)->run;
+		run = &arena_miscelm_get(chunk, pageind+npages)->run;
 		arena_run_split_large(arena, run, splitsize, zero);
 
 		size = oldsize + splitsize;