diff --git a/svc/routes/product_images.go b/svc/routes/product_images.go
index cd35e80..1538a69 100644
--- a/svc/routes/product_images.go
+++ b/svc/routes/product_images.go
@@ -77,6 +77,22 @@ func firstThreeDigitToken(tokens []string) string {
 	return ""
 }
 
+func filePrimaryMatchesDim1(fileName, dim1 string) bool {
+	dim1 = strings.ToUpper(strings.TrimSpace(dim1))
+	if dim1 == "" {
+		return true
+	}
+	tokens := tokenizeImageFileName(fileName)
+	if len(tokens) == 0 {
+		return true
+	}
+	primary := firstThreeDigitToken(tokens)
+	if primary == "" {
+		return true
+	}
+	return primary == dim1
+}
+
 func imageFileMatches(fileName, dim1, dim3 string) bool {
 	dim1 = strings.ToUpper(strings.TrimSpace(dim1))
 	dim3 = strings.ToUpper(strings.TrimSpace(dim3))
@@ -322,7 +338,7 @@ ORDER BY
 				if len(targetDimval1) > 0 {
 					clustered := make([]ProductImageItem, 0, len(items))
 					for _, it := range items {
-						if _, ok := targetDimval1[rowDim1ByID[it.ID]]; ok {
+						if _, ok := targetDimval1[rowDim1ByID[it.ID]]; ok && filePrimaryMatchesDim1(it.FileName, dim1Upper) {
 							clustered = append(clustered, it)
 						}
 					}