diff --git a/Outputs/OpenGL/ScanTarget.cpp b/Outputs/OpenGL/ScanTarget.cpp
index 08e1d4fbc..85fa3fe0f 100644
--- a/Outputs/OpenGL/ScanTarget.cpp
+++ b/Outputs/OpenGL/ScanTarget.cpp
@@ -174,6 +174,8 @@ void ScanTarget::end_scan() {
 }
 
 uint8_t *ScanTarget::begin_data(size_t required_length, size_t required_alignment) {
+	assert(required_alignment);
+
 	if(allocation_has_failed_) return nullptr;
 	if(!write_area_texture_.size()) {
 		allocation_has_failed_ = true;