diff --git a/src/intel/isl/isl.c b/src/intel/isl/isl.c
index 94778ac8594..7271ecfbe7d 100644
--- a/src/intel/isl/isl.c
+++ b/src/intel/isl/isl.c
@@ -822,8 +822,8 @@ isl_calc_phys_level0_extent_sa(const struct isl_device *dev,
 {
    const struct isl_format_layout *fmtl = isl_format_get_layout(info->format);
 
-   if (isl_format_is_yuv(info->format))
-      isl_finishme("%s:%s: YUV format", __FILE__, __func__);
+   if (isl_format_is_planar(info->format))
+      unreachable("Planar formats unsupported");
 
    switch (info->dim) {
    case ISL_SURF_DIM_1D:
diff --git a/src/intel/isl/isl.h b/src/intel/isl/isl.h
index f3cb1751ea9..05ab472e468 100644
--- a/src/intel/isl/isl.h
+++ b/src/intel/isl/isl.h
@@ -1623,6 +1623,12 @@ isl_format_has_bc_compression(enum isl_format fmt)
    return false;
 }
 
+static inline bool
+isl_format_is_planar(enum isl_format fmt)
+{
+   return fmt == ISL_FORMAT_PLANAR_420_8;
+}
+
 static inline bool
 isl_format_is_yuv(enum isl_format fmt)
 {