diff --git a/src/DataVampire.cpp b/src/DataVampire.cpp
index 57704aef2300eb9345615f077a8539e6b9055b43..74591919edc64bba8706fca09dedc4b28ec1e251 100644
--- a/src/DataVampire.cpp
+++ b/src/DataVampire.cpp
@@ -2039,7 +2039,7 @@ void DataVampire::store_data(Tango::DeviceData *cmd_value, int32_t num_samples,
 	}
 
 	if ((*attr_PostAcqRoi_read == true) && (roi_dim == 4)) { 
-		if ((num_cols * num_rows * num_samples) != (*attr_Width_read * *attr_Height_read * num_samples)) {
+		if (val.size() != (*attr_Width_read * *attr_Height_read * num_samples)) {
 			Tango::Except::throw_exception (
 				(const char *)"Failed to store data",
 				(const char *)"Width/Height mismatch with image size",