diff --git a/hash.c b/hash.c
index b1296f0018..82f7e24404 100644
--- a/hash.c
+++ b/hash.c
@@ -290,22 +290,32 @@ void git_hash_init(struct git_hash_ctx *ctx, const struct git_hash_algo *algop)
 
 void git_hash_clone(struct git_hash_ctx *dst, const struct git_hash_ctx *src)
 {
+	if (!src->active)
+		BUG("attempt to copy from an inactive hash context");
+	if (!dst->active)
+		BUG("attempt to copy to an inactive hash context");
 	src->algop->clone_fn(dst, src);
 }
 
 void git_hash_update(struct git_hash_ctx *ctx, const void *in, size_t len)
 {
+	if (!ctx->active)
+		BUG("attempt to update an inactive hash context");
 	ctx->algop->update_fn(ctx, in, len);
 }
 
 void git_hash_final(unsigned char *hash, struct git_hash_ctx *ctx)
 {
+	if (!ctx->active)
+		BUG("attempt to finalize an inactive hash context");
 	ctx->algop->final_fn(hash, ctx);
 	ctx->active = false;
 }
 
 void git_hash_final_oid(struct object_id *oid, struct git_hash_ctx *ctx)
 {
+	if (!ctx->active)
+		BUG("attempt to finalize an inactive hash context");
 	ctx->algop->final_oid_fn(oid, ctx);
 	ctx->active = false;
 }