diff --git a/src/allocator.c b/src/allocator.c
index b9b2d02a1..bb0c009fa 100644
--- a/src/allocator.c
+++ b/src/allocator.c
@@ -147,6 +147,11 @@ sixel_allocator_malloc(
     assert(allocator);
     assert(allocator->fn_malloc);
 
+    if (n == 0) {
+        sixel_helper_set_additional_message(
+            "sixel_allocator_malloc: called with n == 0");
+        return NULL;
+    }
     return allocator->fn_malloc(n);
 }