diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 4f6761d..0326cc7 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -2527,6 +2527,13 @@ merge_decls (tree newdecl, tree olddecl, tree newtype, tree oldtype)
     {
       TREE_STATIC (olddecl) = TREE_STATIC (newdecl);
       TREE_PUBLIC (olddecl) = TREE_PUBLIC (newdecl);
+
+      if (TREE_CODE (olddecl) == VAR_DECL
+	 && TREE_CODE (newdecl) == VAR_DECL
+	 && !lookup_attribute ("common", DECL_ATTRIBUTES (newdecl))
+	 && !lookup_attribute ("nocommon", DECL_ATTRIBUTES (newdecl))
+	 && !DECL_COMMON (olddecl))
+	DECL_COMMON (newdecl) = 0;
     }

   if (TREE_CODE (newdecl) == FUNCTION_DECL)