diff --git a/src/mesa/main/formats.c b/src/mesa/main/formats.c
index 6f0ccd01220..19489e84648 100644
--- a/src/mesa/main/formats.c
+++ b/src/mesa/main/formats.c
@@ -645,6 +645,16 @@ _mesa_is_format_astc_2d(mesa_format format)
 }
 
 
+/**
+ * Return TRUE if format is an S3TC compressed format.
+ */
+bool
+_mesa_is_format_s3tc(mesa_format format)
+{
+   return _mesa_get_format_layout(format) == MESA_FORMAT_LAYOUT_S3TC;
+}
+
+
 /**
  * Return TRUE if format is an BPTC compressed format.
  */
diff --git a/src/mesa/main/formats.h b/src/mesa/main/formats.h
index 03baa204380..e8f91389b93 100644
--- a/src/mesa/main/formats.h
+++ b/src/mesa/main/formats.h
@@ -695,6 +695,9 @@ _mesa_is_format_etc2(mesa_format format);
 bool
 _mesa_is_format_astc_2d(mesa_format format);
 
+bool
+_mesa_is_format_s3tc(mesa_format format);
+
 bool
 _mesa_is_format_bptc(mesa_format format);