diff --git a/libvips/colour/profile_load.c b/libvips/colour/profile_load.c
index a4964c7a..9f9016c7 100644
--- a/libvips/colour/profile_load.c
+++ b/libvips/colour/profile_load.c
@@ -104,7 +104,7 @@ vips_fallback_profile_get( const char *name, size_t *length )
 	for( p = vips_fallback_profile_list; p; p = p->next ) {
 		VipsFallbackProfile *fallback = (VipsFallbackProfile *) p->data;
 
-		if( strcasecmp( fallback->name, name ) == 0 ) {
+		if( g_ascii_strcasecmp( fallback->name, name ) == 0 ) {
 			*length = fallback->data_length;
 
 			return( fallback->data );
@@ -128,7 +128,7 @@ vips_profile_load_build( VipsObject *object )
 		build( object ) )
 		return( -1 );
 
-	if( strcasecmp( load->name, "none" ) == 0 ) {
+	if( g_ascii_strcasecmp( load->name, "none" ) == 0 ) {
 		profile = NULL;
 	}
 	else if( (data = vips_fallback_profile_get( load->name, &length )) ) {
diff --git a/libvips/deprecated/vips7compat.c b/libvips/deprecated/vips7compat.c
index 8a925ad1..308220b7 100644
--- a/libvips/deprecated/vips7compat.c
+++ b/libvips/deprecated/vips7compat.c
@@ -606,7 +606,7 @@ lookup_enum( GType type, const char *names[], const char *name )
 		return( value->value );
 
 	for( i = 0; names[i]; i++ )
-		if( strcasecmp( names[i], name ) == 0 )
+		if( g_ascii_strcasecmp( names[i], name ) == 0 )
 			return( i );
 
 	return( -1 );
diff --git a/libvips/foreign/dzsave.c b/libvips/foreign/dzsave.c
index 65ea028b..9f0d761d 100644
--- a/libvips/foreign/dzsave.c
+++ b/libvips/foreign/dzsave.c
@@ -2198,16 +2198,16 @@ vips_foreign_save_dz_file_build( VipsObject *object )
 	 */
 	if( (p = strrchr( dz->basename, '.' )) ) {
 		if( !vips_object_argument_isset( object, "container" ) ) 
-			if( strcasecmp( p + 1, "zip" ) == 0 ||
-				strcasecmp( p + 1, "szi" ) == 0 ) 
+			if( g_ascii_strcasecmp( p + 1, "zip" ) == 0 ||
+				g_ascii_strcasecmp( p + 1, "szi" ) == 0 ) 
 				dz->container = VIPS_FOREIGN_DZ_CONTAINER_ZIP;
 
 		/* Remove any legal suffix. We don't remove all suffixes
 		 * since we might be writing to a dirname with a dot in.
 		 */
-		if( strcasecmp( p + 1, "zip" ) == 0 ||
-			strcasecmp( p + 1, "szi" ) == 0 || 
-			strcasecmp( p + 1, "dz" ) == 0 )
+		if( g_ascii_strcasecmp( p + 1, "zip" ) == 0 ||
+			g_ascii_strcasecmp( p + 1, "szi" ) == 0 || 
+			g_ascii_strcasecmp( p + 1, "dz" ) == 0 )
 			*p = '\0';
 	}
 
diff --git a/libvips/foreign/heifload.c b/libvips/foreign/heifload.c
index 4f6d8826..d15a81a3 100644
--- a/libvips/foreign/heifload.c
+++ b/libvips/foreign/heifload.c
@@ -302,7 +302,7 @@ vips_foreign_load_heif_set_header( VipsForeignLoadHeif *heif, VipsImage *out )
 		/* We need to skip the first four bytes of EXIF, they just
 		 * contain the offset.
 		 */
-		if( strcasecmp( type, "exif" ) == 0 ) {
+		if( g_ascii_strcasecmp( type, "exif" ) == 0 ) {
 			data += 4;
 			length -= 4;
 		}
@@ -312,9 +312,9 @@ vips_foreign_load_heif_set_header( VipsForeignLoadHeif *heif, VipsImage *out )
 		 * XMP metadata is just attached with the "mime" type, and
 		 * usually start with "<x:xmpmeta".
 		 */
-		if( strcasecmp( type, "exif" ) == 0 )
+		if( g_ascii_strcasecmp( type, "exif" ) == 0 )
 			vips_snprintf( name, 256, VIPS_META_EXIF_NAME );
-		else if( strcasecmp( type, "mime" ) == 0 &&
+		else if( g_ascii_strcasecmp( type, "mime" ) == 0 &&
 			vips_isprefix( "<x:xmpmeta", (const char *) data ) ) 
 			snprintf( name, 256, VIPS_META_XMP_NAME ); 
 		else
@@ -323,7 +323,7 @@ vips_foreign_load_heif_set_header( VipsForeignLoadHeif *heif, VipsImage *out )
 		vips_image_set_blob( out, name, 
 			(VipsCallbackFn) NULL, data, length );
 
-		if( strcasecmp( type, "exif" ) == 0 )
+		if( g_ascii_strcasecmp( type, "exif" ) == 0 )
 			(void) vips__exif_parse( out );
 	}
 
diff --git a/libvips/foreign/vipspng.c b/libvips/foreign/vipspng.c
index a890b0be..2d1cddfd 100644
--- a/libvips/foreign/vipspng.c
+++ b/libvips/foreign/vipspng.c
@@ -1077,7 +1077,8 @@ write_vips( Write *write,
 				return( -1 );
 			if( blob ) {
 				size_t length;
-				const void *data = vips_blob_get( blob, &length );
+				const void *data 
+					= vips_blob_get( blob, &length );
 
 #ifdef DEBUG
 				printf( "write_vips: attaching %zd bytes "
@@ -1086,7 +1087,7 @@ write_vips( Write *write,
 
 				png_set_iCCP( write->pPng, write->pInfo, 
 					"icc", PNG_COMPRESSION_TYPE_BASE, 
-					data, length );
+					(void *) data, length );
 
 				vips_area_unref( (VipsArea *) blob );
 			}
@@ -1105,7 +1106,8 @@ write_vips( Write *write,
 #endif /*DEBUG*/
 
 			png_set_iCCP( write->pPng, write->pInfo, "icc",
-				PNG_COMPRESSION_TYPE_BASE, data, length );
+				PNG_COMPRESSION_TYPE_BASE, 
+				(void *) data, length );
 
 		}
 
diff --git a/libvips/iofuncs/object.c b/libvips/iofuncs/object.c
index 8c7a9e99..c6f1050b 100644
--- a/libvips/iofuncs/object.c
+++ b/libvips/iofuncs/object.c
@@ -1988,8 +1988,8 @@ vips_object_set_argument_from_string( VipsObject *object,
 
 		b = TRUE;
 		if( value &&
-			(strcasecmp( value, "false" ) == 0 ||
-			strcasecmp( value, "no" ) == 0 ||
+			(g_ascii_strcasecmp( value, "false" ) == 0 ||
+			g_ascii_strcasecmp( value, "no" ) == 0 ||
 			strcmp( value, "0" ) == 0) )
 			b = FALSE;
 
@@ -2804,12 +2804,12 @@ vips_type_depth( GType type )
 static void *
 test_name( VipsObjectClass *class, const char *nickname )
 {
-	if( strcasecmp( class->nickname, nickname ) == 0 )
+	if( g_ascii_strcasecmp( class->nickname, nickname ) == 0 )
 		return( class );
 
 	/* Check the class name too, why not.
 	 */
-	if( strcasecmp( G_OBJECT_CLASS_NAME( class ), nickname ) == 0 )
+	if( g_ascii_strcasecmp( G_OBJECT_CLASS_NAME( class ), nickname ) == 0 )
 		return( class );
 
 	return( NULL );
diff --git a/libvips/iofuncs/util.c b/libvips/iofuncs/util.c
index b715403b..e0eeb734 100644
--- a/libvips/iofuncs/util.c
+++ b/libvips/iofuncs/util.c
@@ -333,7 +333,7 @@ vips_iscasepostfix( const char *a, const char *b )
 	if( n > m )
 		return( FALSE );
 
-	return( strcasecmp( a + m - n, b ) == 0 );
+	return( g_ascii_strcasecmp( a + m - n, b ) == 0 );
 }
 
 /* Test for string a starts string b. a is a known-good string, b may be