diff --git a/libvips/foreign/gifload.c b/libvips/foreign/gifload.c
index 4f6a4483..122e5f40 100644
--- a/libvips/foreign/gifload.c
+++ b/libvips/foreign/gifload.c
@@ -571,7 +571,7 @@ vips_foreign_load_gif_set_header( VipsForeignLoadGif *gif, VipsImage *image )
 		1.0, 1.0 );
 	vips_image_pipelinev( image, VIPS_DEMAND_STYLE_FATSTRIP, NULL );
 
-	if( gif->n > 1 ) 
+	if( vips_object_argument_isset( VIPS_OBJECT( gif ), "n" ) )
 		vips_image_set_int( image, 
 			VIPS_META_PAGE_HEIGHT, gif->file->SHeight );
 	vips_image_set_int( image, VIPS_META_N_PAGES, gif->n_pages );
diff --git a/libvips/foreign/heifload.c b/libvips/foreign/heifload.c
index d475b076..73bceab2 100644
--- a/libvips/foreign/heifload.c
+++ b/libvips/foreign/heifload.c
@@ -382,7 +382,7 @@ vips_foreign_load_heif_set_header( VipsForeignLoadHeif *heif, VipsImage *out )
 
 	vips_image_set_int( out, "heif-primary", heif->primary_page );
 	vips_image_set_int( out, "n-pages", heif->n_top );
-	if( heif->n > 1 )
+	if( vips_object_argument_isset( VIPS_OBJECT( heif ), "n" ) )
 		vips_image_set_int( out, 
 			VIPS_META_PAGE_HEIGHT, heif->page_height );
 
diff --git a/libvips/foreign/magick7load.c b/libvips/foreign/magick7load.c
index 3167f30b..6592ff74 100644
--- a/libvips/foreign/magick7load.c
+++ b/libvips/foreign/magick7load.c
@@ -595,7 +595,7 @@ vips_foreign_load_magick7_parse( VipsForeignLoadMagick7 *magick7,
 
 	/* So we can finally set the height.
 	 */
-	if( magick7->n_frames > 1 ) {
+	if( vips_object_argument_isset( VIPS_OBJECT( magick7 ), "n" ) ) {
 		vips_image_set_int( out, VIPS_META_PAGE_HEIGHT, out->Ysize );
 		out->Ysize *= magick7->n_frames;
 	}
diff --git a/libvips/foreign/niftiload.c b/libvips/foreign/niftiload.c
index cd90ab4b..11461843 100644
--- a/libvips/foreign/niftiload.c
+++ b/libvips/foreign/niftiload.c
@@ -505,7 +505,7 @@ vips_foreign_load_nifti_set_header( VipsForeignLoadNifti *nifti,
 		vips_image_set_blob_copy( out, txt, ext->edata, ext->esize );
 	}
 
-	if( nim->ny > 1 )
+	if( vips_object_argument_isset( VIPS_OBJECT( nifti ), "n" ) )
 		vips_image_set_int( out, VIPS_META_PAGE_HEIGHT, nim->ny );
 
 	return( 0 );
diff --git a/libvips/foreign/pdfiumload.c b/libvips/foreign/pdfiumload.c
index f0a022f0..4deb2ba0 100644
--- a/libvips/foreign/pdfiumload.c
+++ b/libvips/foreign/pdfiumload.c
@@ -363,8 +363,7 @@ vips_foreign_load_pdf_header( VipsForeignLoad *load )
 	for( i = 1; i < pdf->n; i++ ) 
 		if( pdf->pages[i].height != pdf->pages[0].height )
 			break;
-	if( i == pdf->n &&
-		pdf->n > 1 ) 
+	if( vips_object_argument_isset( VIPS_OBJECT( pdf ), "n" ) )
 		vips_image_set_int( load->out, 
 			VIPS_META_PAGE_HEIGHT, pdf->pages[0].height );
 
diff --git a/libvips/foreign/pdfload.c b/libvips/foreign/pdfload.c
index 86c1d992..1a6e5b74 100644
--- a/libvips/foreign/pdfload.c
+++ b/libvips/foreign/pdfload.c
@@ -317,8 +317,7 @@ vips_foreign_load_pdf_header( VipsForeignLoad *load )
 	for( i = 1; i < pdf->n; i++ ) 
 		if( pdf->pages[i].height != pdf->pages[0].height )
 			break;
-	if( i == pdf->n &&
-		pdf->n > 1 ) 
+	if( vips_object_argument_isset( VIPS_OBJECT( pdf ), "n" ) )
 		vips_image_set_int( load->out, 
 			VIPS_META_PAGE_HEIGHT, pdf->pages[0].height );