diff --git a/libvips/foreign/svgload.c b/libvips/foreign/svgload.c
index 212c76a7..d8d06a38 100644
--- a/libvips/foreign/svgload.c
+++ b/libvips/foreign/svgload.c
@@ -211,7 +211,7 @@ vips_foreign_load_svg_is_a( const void *buf, size_t len )
 	 * before the <svg line.
 	 *
 	 * Simple rules:
-	 * - first 24 chars are plain ascii
+	 * - first 24 chars are plain ascii (x09-x7F)
 	 * - first SVG_HEADER_SIZE chars contain "<svg", upper or lower case.
 	 *
 	 * We could rsvg_handle_new_from_data() on the buffer, but that can be
@@ -220,7 +220,7 @@ vips_foreign_load_svg_is_a( const void *buf, size_t len )
 	if( len < 24 )
 		return( 0 );
 	for( i = 0; i < 24; i++ )
-		if( !isascii( str[i] ) )
+		if( !isascii( str[i] ) || str[i] < 9 )
 			return( FALSE );
 	for( i = 0; i < SVG_HEADER_SIZE && i < len - 5; i++ )
 		if( g_ascii_strncasecmp( str + i, "<svg", 4 ) == 0 )
diff --git a/test/test-suite/helpers/helpers.py b/test/test-suite/helpers/helpers.py
index e5645713..8d1c309d 100644
--- a/test/test-suite/helpers/helpers.py
+++ b/test/test-suite/helpers/helpers.py
@@ -21,6 +21,7 @@ OME_FILE = os.path.join(IMAGES, "multi-channel-z-series.ome.tif")
 ANALYZE_FILE = os.path.join(IMAGES, "t00740_tr1_segm.hdr")
 GIF_FILE = os.path.join(IMAGES, "cramps.gif")
 WEBP_FILE = os.path.join(IMAGES, "1.webp")
+WEBP_LOOKS_LIKE_SVG_FILE = os.path.join(IMAGES, "looks-like-svg.webp")
 EXR_FILE = os.path.join(IMAGES, "sample.exr")
 FITS_FILE = os.path.join(IMAGES, "WFPC2u5780205r_c0fx.fits")
 OPENSLIDE_FILE = os.path.join(IMAGES, "CMU-1-Small-Region.svs")
diff --git a/test/test-suite/images/looks-like-svg.webp b/test/test-suite/images/looks-like-svg.webp
new file mode 100644
index 00000000..f5056005
Binary files /dev/null and b/test/test-suite/images/looks-like-svg.webp differ
diff --git a/test/test-suite/test_foreign.py b/test/test-suite/test_foreign.py
index 182f8af8..9f3386ab 100644
--- a/test/test-suite/test_foreign.py
+++ b/test/test-suite/test_foreign.py
@@ -17,7 +17,7 @@ from helpers import \
     GIF_ANIM_DISPOSE_PREVIOUS_FILE, \
     GIF_ANIM_DISPOSE_PREVIOUS_EXPECTED_PNG_FILE, \
     temp_filename, assert_almost_equal_objects, have, skip_if_no, \
-    TIF1_FILE, TIF2_FILE, TIF4_FILE
+    TIF1_FILE, TIF2_FILE, TIF4_FILE, WEBP_LOOKS_LIKE_SVG_FILE
 
 
 class TestForeign:
@@ -676,6 +676,11 @@ class TestForeign:
             assert x1.get("page-height") == x2.get("page-height")
             assert x1.get("gif-loop") == x2.get("gif-loop")
 
+        # WebP image that happens to contain the string "<svg"
+        if have("svgload"):
+            x = pyvips.Image.new_from_file(WEBP_LOOKS_LIKE_SVG_FILE)
+            assert x.get("vips-loader") == "webpload"
+
     @skip_if_no("analyzeload")
     def test_analyzeload(self):
         def analyze_valid(im):