diff --git a/libvips/foreign/ppmload.c b/libvips/foreign/ppmload.c
index b38fc281..24c02849 100644
--- a/libvips/foreign/ppmload.c
+++ b/libvips/foreign/ppmload.c
@@ -64,7 +64,7 @@
 
 /* TODO
  *
- * - load filename streams with mmap ... we'll need to add get_flags_stream
+ * - load filename streams with mmap 
  */
 
 /*
@@ -330,22 +330,25 @@ vips_foreign_load_ppm_parse_header( VipsForeignLoadPpm *ppm )
 static VipsForeignFlags
 vips_foreign_load_ppm_get_flags( VipsForeignLoad *load )
 {
+	VipsForeignLoadPpm *ppm = (VipsForeignLoadPpm *) load;
+
 	VipsForeignFlags flags;
 
 	flags = 0;
 
-	/* reenable this when mmap load goes back in
-	 * 
-	VipsForeignLoadPpm *ppm = (VipsForeignLoadPpm *) load;
-
+	/* If this streami supports fast mmap and this PPM is >=8 bit binary,
+	 * then we can mmap the file and support partial load. Otherwise,
+	 * it's sequential.
+	 */
 	if( !ppm->have_read_header &&
 		vips_foreign_load_ppm_parse_header( ppm ) )
 		return( 0 );
-	if( !ppm->ascii && ppm->bits >= 8 )
+	if( vips_streami_is_mappable( ppm->streami ) &&
+		!ppm->ascii && 
+		ppm->bits >= 8 )
 		flags |= VIPS_FOREIGN_PARTIAL;
-	 */
-
-	flags |= VIPS_FOREIGN_SEQUENTIAL;
+	else
+		flags |= VIPS_FOREIGN_SEQUENTIAL;
 
 	return( flags );
 }
@@ -388,7 +391,9 @@ vips_foreign_load_ppm_header( VipsForeignLoad *load )
 }
 
 /* Read a ppm/pgm file using mmap().
-load_mmap( VipsForeignLoadPpm *ppm, VipsImage *image )
+ */
+static int
+vips_foreign_load_ppm_map( VipsForeignLoadPpm *ppm, VipsImage *image )
 {
 	VipsImage **t = (VipsImage **)
                 vips_object_local_array( VIPS_OBJECT( ppm ), 3 );
@@ -400,7 +405,8 @@ load_mmap( VipsForeignLoadPpm *ppm, VipsImage *image )
 	vips_streamib_unbuffer( ppm->streamib );
 	header_offset = vips_streami_seek( ppm->streami, 0, SEEK_CUR );
 	data = vips_streami_map( ppm->streami, &length );
-	if( header_offset < 0 || !data )
+	if( header_offset < 0 || 
+		!data )
 		return( -1 );
 	data += header_offset;
        	length -= header_offset;
@@ -416,7 +422,6 @@ load_mmap( VipsForeignLoadPpm *ppm, VipsImage *image )
 
 	return( 0 );
 }
- */
 
 static int
 vips_foreign_load_ppm_generate_binary( VipsRegion *or, 
@@ -556,34 +561,46 @@ vips_foreign_load_ppm_load( VipsForeignLoad *load )
 	VipsImage **t = (VipsImage **) 
 		vips_object_local_array( (VipsObject *) load, 2 );
 
-	VipsGenerateFn generate;
-
 	if( !ppm->have_read_header &&
 		vips_foreign_load_ppm_parse_header( ppm ) )
 		return( 0 );
 
-	/* What sort of read are we doing?
+	/* If the stream is mappable and this is a binary file, we can map it.
 	 */
-	if( !ppm->ascii && ppm->bits >= 8 ) {
-		generate = vips_foreign_load_ppm_generate_binary;
-
-		/* The binary loader does not use the buffered IO object.
-		 */
-		vips_streamib_unbuffer( ppm->streamib ); 
+	if( vips_streami_is_mappable( ppm->streami ) &&
+		!ppm->ascii && 
+		ppm->bits >= 8 ) {
+		if( vips_foreign_load_ppm_map( ppm, load->real ) )
+			return( -1 );
 	}
-	else if( !ppm->ascii && ppm->bits == 1 )
-		generate = vips_foreign_load_ppm_generate_1bit_binary;
-	else if( ppm->ascii && ppm->bits == 1 )
-		generate = vips_foreign_load_ppm_generate_1bit_ascii;
-	else 
-		generate = vips_foreign_load_ppm_generate_ascii_int;
+	else {
+		VipsGenerateFn generate;
 
-	t[0] = vips_image_new(); 
-	vips_foreign_load_ppm_set_image( ppm, t[0] );
-	if( vips_image_generate( t[0], NULL, generate, NULL, ppm, NULL ) ||
-		vips_sequential( t[0], &t[1], NULL ) ||
-		vips_image_write( t[1], load->real ) ) 
-		return( -1 );
+		/* What sort of read are we doing?
+		 */
+		if( !ppm->ascii && ppm->bits >= 8 ) {
+			generate = vips_foreign_load_ppm_generate_binary;
+
+			/* The binary loader does not use the buffered IO 
+			 * object.
+			 */
+			vips_streamib_unbuffer( ppm->streamib ); 
+		}
+		else if( !ppm->ascii && ppm->bits == 1 )
+			generate = vips_foreign_load_ppm_generate_1bit_binary;
+		else if( ppm->ascii && ppm->bits == 1 )
+			generate = vips_foreign_load_ppm_generate_1bit_ascii;
+		else 
+			generate = vips_foreign_load_ppm_generate_ascii_int;
+
+		t[0] = vips_image_new(); 
+		vips_foreign_load_ppm_set_image( ppm, t[0] );
+		if( vips_image_generate( t[0], 
+				NULL, generate, NULL, ppm, NULL ) ||
+			vips_sequential( t[0], &t[1], NULL ) ||
+			vips_image_write( t[1], load->real ) ) 
+			return( -1 );
+	}
 
 	if( vips_streami_decode( ppm->streami ) )
 		return( -1 );
diff --git a/libvips/include/vips/foreign.h b/libvips/include/vips/foreign.h
index a585a851..4ce3d451 100644
--- a/libvips/include/vips/foreign.h
+++ b/libvips/include/vips/foreign.h
@@ -197,7 +197,8 @@ typedef struct _VipsForeignLoadClass {
 	 * of flags. If you don't define it, vips will default to 0 (no flags 
 	 * set).  
 	 *
-	 * This operation is necessary for vips7 compatibility. 
+	 * This method is necessary for vips7 compatibility. Don't define
+	 * it if you don't need vips7.
 	 */
 	VipsForeignFlags (*get_flags_filename)( const char *filename );
 
@@ -217,8 +218,7 @@ typedef struct _VipsForeignLoadClass {
 	 * @header() needs to set the dhint on the image .. otherwise you get 
 	 * the default SMALLTILE.
 	 *
-	 * Return 0 for success, -1 for error, setting
-	 * vips_error().
+	 * Return 0 for success, -1 for error, setting vips_error().
 	 */
 	int (*header)( VipsForeignLoad *load );
 
diff --git a/libvips/include/vips/stream.h b/libvips/include/vips/stream.h
index 533f13c6..ee2d1855 100644
--- a/libvips/include/vips/stream.h
+++ b/libvips/include/vips/stream.h
@@ -209,6 +209,7 @@ int vips_streami_unminimise( VipsStreami *streami );
 int vips_streami_decode( VipsStreami *streami );
 ssize_t vips_streami_read( VipsStreami *streami, void *data, size_t length );
 const void *vips_streami_map( VipsStreami *streami, size_t *length );
+gboolean vips_streami_is_mappable( VipsStreami *streami );
 gint64 vips_streami_seek( VipsStreami *streami, gint64 offset, int whence );
 int vips_streami_rewind( VipsStreami *streami );
 size_t vips_streami_sniff_at_most( VipsStreami *streami, 
diff --git a/libvips/iofuncs/streami.c b/libvips/iofuncs/streami.c
index 8f5760ac..c0fa9da9 100644
--- a/libvips/iofuncs/streami.c
+++ b/libvips/iofuncs/streami.c
@@ -817,10 +817,11 @@ vips_streami_descriptor_to_memory( VipsStreami *streami )
  * @streami: input stream to operate on
  * @length_out: return the file length here, or NULL
  *
- * Map the stream object entirely into memory, and return a pointer to the
+ * Map the stream object entirely into memory and return a pointer to the
  * start. If @length_out is non-NULL, the file size if written to it.
  *
- * This operation can take a long time.
+ * This operation can take a long time. Use vips_streami_is_mappable() to 
+ * check if a streami can be mapped efficiently.
  *
  * Returns: a pointer to the start of the file contents, or NULL on error.
  */
@@ -860,6 +861,30 @@ vips_streami_map( VipsStreami *streami, size_t *length_out )
 	return( streami->data );
 }
 
+/**
+ * vips_streami_map:
+ * @streami: input stream to operate on
+ * @length_out: return the file length here, or NULL
+ *
+ * Map the stream object entirely into memory and return a pointer to the
+ * start. If @length_out is non-NULL, the file size if written to it.
+ *
+ * This operation can take a long time. Use vips_streami_is_mappable() to check
+ * if a streami can be mapped efficiently.
+ *
+ * Returns: a pointer to the start of the file contents, or NULL on error.
+ */
+gboolean 
+vips_streami_is_mappable( VipsStreami *streami )
+{
+	/* Already a memory object, or there's a filename we can map, or
+	 * there's a seekable descriptor.
+	 */
+	return( streami->data ||
+		VIPS_STREAM( streami )->filename ||
+		(streami->is_pipe && VIPS_STREAM( streami )->descriptor) );
+}
+
 /**
  * vips_streami_seek:
  * @streami: input stream to operate on