diff --git a/cutils.c b/cutils.c
index a02fb76..b447e6a 100644
--- a/cutils.c
+++ b/cutils.c
@@ -140,8 +140,10 @@ int dbuf_put(DynBuf *s, const uint8_t *data, size_t len)
         if (dbuf_realloc(s, s->size + len))
             return -1;
     }
-    memcpy(s->buf + s->size, data, len);
-    s->size += len;
+    if (len > 0) {
+        memcpy(s->buf + s->size, data, len);
+        s->size += len;
+    }
     return 0;
 }
 
diff --git a/libbf.c b/libbf.c
index fe1628e..dc00328 100644
--- a/libbf.c
+++ b/libbf.c
@@ -292,7 +292,8 @@ int bf_set(bf_t *r, const bf_t *a)
     }
     r->sign = a->sign;
     r->expn = a->expn;
-    memcpy(r->tab, a->tab, a->len * sizeof(limb_t));
+    if (a->len > 0)
+        memcpy(r->tab, a->tab, a->len * sizeof(limb_t));
     return 0;
 }
 
diff --git a/quickjs-libc.c b/quickjs-libc.c
index e180dd0..12dc798 100644
--- a/quickjs-libc.c
+++ b/quickjs-libc.c
@@ -3462,7 +3462,8 @@ static JSValue js_worker_postMessage(JSContext *ctx, JSValueConst this_val,
     msg->sab_tab = malloc(sizeof(msg->sab_tab[0]) * sab_tab_len);
     if (!msg->sab_tab)
         goto fail;
-    memcpy(msg->sab_tab, sab_tab, sizeof(msg->sab_tab[0]) * sab_tab_len);
+    if (sab_tab_len > 0)
+        memcpy(msg->sab_tab, sab_tab, sizeof(msg->sab_tab[0]) * sab_tab_len);
     msg->sab_tab_len = sab_tab_len;
 
     js_free(ctx, data);
diff --git a/quickjs.c b/quickjs.c
index 16c6760..b0e91d0 100644
--- a/quickjs.c
+++ b/quickjs.c
@@ -32595,8 +32595,10 @@ static JSValue js_create_function(JSContext *ctx, JSFunctionDef *fd)
             }
         } else {
             b->vardefs = (void *)((uint8_t*)b + vardefs_offset);
-            memcpy(b->vardefs, fd->args, fd->arg_count * sizeof(fd->args[0]));
-            memcpy(b->vardefs + fd->arg_count, fd->vars, fd->var_count * sizeof(fd->vars[0]));
+            if (fd->arg_count > 0)
+                memcpy(b->vardefs, fd->args, fd->arg_count * sizeof(fd->args[0]));
+            if (fd->var_count > 0)
+                memcpy(b->vardefs + fd->arg_count, fd->vars, fd->var_count * sizeof(fd->vars[0]));
         }
         b->var_count = fd->var_count;
         b->arg_count = fd->arg_count;