diff --git a/ChangeLog b/ChangeLog
index 3cd3234b..7ac84db3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,6 @@
 30/4/21 start 8.10.7
 - better vips7 PNG load compatibility [SkyDiverCool]
+- fix load of large PPM images from a pipe [ewelot]
 
 22/12/20 start 8.10.6
 - don't seek on bad file descriptors [kleisauke]
diff --git a/libvips/foreign/ppmload.c b/libvips/foreign/ppmload.c
index 7f16cb65..083b2a56 100644
--- a/libvips/foreign/ppmload.c
+++ b/libvips/foreign/ppmload.c
@@ -506,8 +506,8 @@ vips_foreign_load_ppm_generate_binary( VipsRegion *or,
 		while( n_bytes > 0 ) {
 			gint64 bytes_read;
 
-			bytes_read = vips_source_read( ppm->source, 
-				q, sizeof_line );
+			bytes_read = 
+				vips_source_read( ppm->source, q, n_bytes );
 			if( bytes_read < 0 ) 
 				return( -1 );
 			if( bytes_read == 0 ) {
@@ -516,8 +516,8 @@ vips_foreign_load_ppm_generate_binary( VipsRegion *or,
 				return( -1 );
 			}
 
-			n_bytes -= bytes_read;
 			q += bytes_read;
+			n_bytes -= bytes_read;
 		}
 	}