diff --git a/runtime/host.h b/runtime/host.h
index d46336b9..7bcc152a 100644
--- a/runtime/host.h
+++ b/runtime/host.h
@@ -262,7 +262,8 @@ uint64_t res_heap_extra_bytes(void);                       // added to the appli
 uint64_t res_heap_extra_kib(void);                         // added to the HeapDef texture heap and its parent; 0 = none
 uint64_t res_tex_heap_extra_bytes(void);                   // TOTK_TEX_HEAP_EXTRA_MB: added to the application pool and
                                                            // the heap cap (mem_init), 2 MiB steps; 0 = none
-int res_tex_heap_from_mod(void);                           // a switched-on mod's HeapDef grows the texture heap
+int res_heapdef_tex_grown(const void *in, size_t n);       // the HeapDef table (.byml.zs) grows TextureHeap over the
+                                                           // shipped size (an HD texture pack's)
 int res_heapdef_build(const void *in, size_t n, void **out, size_t *out_n);   // the HeapDef table (.byml.zs) with
                                                            // the grown heaps, malloc'd; 0 = cannot (logged)
 void res_heapdef_served(void);                             // romfs.c serves the grown table
diff --git a/runtime/resolution.c b/runtime/resolution.c
index ac4fa75c..20b73d06 100644
--- a/runtime/resolution.c
+++ b/runtime/resolution.c
@@ -293,22 +293,31 @@ static int heapdef_open(const void *in, size_t n, Byml *b, uint32_t *heaps, cons
 #define HEAPDEF_REL "System/HeapSize/Product.Nin_NX_NVN.HeapDef.byml.zs"
 static struct { int done; uint64_t kib; } MT;
 
-static void mod_heapdef(const char *name, const char *romfs, void *ctx) {
-    (void)ctx;
-    char path[2300];
-    if (snprintf(path, sizeof path, "%s/%s", romfs, HEAPDEF_REL) >= (int)sizeof path) return;
-    uint64_t n = 0;
-    uint8_t *in = plat_file_read(path, &n);
-    if (!in) return;
+// "TextureHeap" of the HeapDef table in[0..n) in KiB; 0 when the table cannot be read or has no such size (the failure
+// is logged with why).
+static int32_t heapdef_tex_kib(const void *in, size_t n, const char *why) {
     Byml b;
     uint32_t heaps;
     size_t th_at = 0;
     int32_t th = 0;
-    if (heapdef_open(in, (size_t)n, &b, &heaps, "its texture heap is left out") &&
-        (th_at = heap_size_field(&b, heaps, "TextureHeap")))
-        memcpy(&th, b.p + th_at, 4);
+    if (!heapdef_open(in, n, &b, &heaps, why)) return 0;
+    if ((th_at = heap_size_field(&b, heaps, "TextureHeap"))) memcpy(&th, b.p + th_at, 4);
+    else rt_log("resolution: the HeapDef table has no TextureHeap size; %s", why);
     free(b.p);
+    return th;
+}
+
+static void mod_heapdef(const char *name, const char *romfs, void *ctx) {
+    (void)ctx;
+    char path[2300], why[400];
+    if (snprintf(path, sizeof path, "%s/%s", romfs, HEAPDEF_REL) >= (int)sizeof path) return;
+    uint64_t n = 0;
+    uint8_t *in = plat_file_read(path, &n);
+    if (!in) return;
+    snprintf(why, sizeof why, "mod %s: its texture heap growth is left out", name);
+    int32_t th = heapdef_tex_kib(in, (size_t)n, why);
     free(in);
+    if (!th) return;
     int64_t grow = (int64_t)th - (int64_t)TEX_HEAP_KIB;
     if (grow > (int64_t)(4096u << 10)) grow = 4096u << 10;
     if (grow > 0 && (uint64_t)grow > MT.kib) MT.kib = (uint64_t)grow;
@@ -321,7 +330,11 @@ static uint64_t mod_tex_heap_kib(void) {
     return MT.kib;
 }
 
-int res_tex_heap_from_mod(void) { return mod_tex_heap_kib() > 0; }
+// Only such a table is swapped for the game's own (romfs.c heapdef_overlay): a mod table that changes other heaps
+// keeps them. A table it cannot read stays the base (logged).
+int res_heapdef_tex_grown(const void *in, size_t n) {
+    return heapdef_tex_kib(in, n, "the mod's table stays the base") > (int32_t)TEX_HEAP_KIB;
+}
 
 int res_heapdef_build(const void *in, size_t n, void **out, size_t *out_n) {
     uint64_t extra = res_heap_extra_kib(), tex = tex_heap_extra_kib();
diff --git a/runtime/romfs.c b/runtime/romfs.c
index 38de9ab2..484c6c0d 100644
--- a/runtime/romfs.c
+++ b/runtime/romfs.c
@@ -533,9 +533,8 @@ static void added_init(void) {
     rt_log("RomFS overlay: %zu files added to the RomFS", nadded);
 }
 
-// RomFS file `rel` as the game would read it: from an overlay that replaces it (*base), else from the image. malloc'd;
-// NULL when it is missing, unreadable or 16 MiB or more (logged with `keeps`, what the game does without it).
-// RomFS file rel as the RomFS holds it, whatever overlays replace it; NULL (logged) when it cannot be read.
+// RomFS file `rel` as the image holds it, whatever overlays replace it. malloc'd; NULL when it is missing, unreadable
+// or 16 MiB or more (logged with `keeps`, what the game does without it).
 static void *read_original(const char *rel, size_t *n, const char *keeps) {
     uint64_t i = lower(rel);
     if (i >= file_count || strcmp(entry_name(entry(i)), rel)) return NULL;
@@ -550,6 +549,8 @@ static void *read_original(const char *rel, size_t *n, const char *keeps) {
     return in;
 }
 
+// RomFS file `rel` as the game would read it: from an overlay that replaces it (*base), else from the image. malloc'd;
+// NULL when it is missing, unreadable or 16 MiB or more (logged with `keeps`, what the game does without it).
 static void *read_served(const char *rel, Overlay **base, size_t *n, const char *keeps) {
     uint64_t i = lower(rel);
     *base = NULL;
@@ -846,9 +847,10 @@ static void restbl_overlay(void) {
 
 // The HeapDef table a bigger game resolution or TOTK_TEX_HEAP_EXTRA_MB needs (resolution.c): its texture heaps and
 // their parents grow. The base is an overlay that replaces the table (a mod's heap sizes stay), else the RomFS
-// original; the grown table is written to <profile>/resolution/ and served in the base's place. A mod's table whose
-// texture heap is grown (an HD texture pack's, resolution.c mod_tex_heap_kib) is not the base: that growth is already
-// in the amount, so the RomFS original grows by it and is served in the mod's place.
+// original; the grown table is written to <profile>/resolution/ and served in the base's place. A served mod table
+// whose own TextureHeap is grown (an HD texture pack's, resolution.c res_heapdef_tex_grown) is not the base: its
+// growth is already in the amount (resolution.c mod_tex_heap_kib), so the RomFS original grows by it and is served in
+// the mod's place. A mod table that changes other heaps only stays the base.
 #define HEAPDEF "System/HeapSize/Product.Nin_NX_NVN.HeapDef.byml.zs"
 static void heapdef_overlay(void) {
     if (!res_heap_extra_kib() && !res_tex_heap_extra_bytes()) return;
@@ -857,11 +859,12 @@ static void heapdef_overlay(void) {
     size_t n;
     void *in = read_served(HEAPDEF, &base, &n, keeps), *out = NULL;
     size_t out_n = 0;
-    if (in && base && base->mod && res_tex_heap_from_mod()) {
+    if (in && base && base->mod && res_heapdef_tex_grown(in, n)) {
         free(in);
         in = read_original(HEAPDEF, &n, keeps);
-        rt_log("RomFS: %s: the game's own HeapDef with the mod's texture heap growth in place of the mod's table",
-               mods_at(base->mod - 1)->name);
+        if (in)
+            rt_log("RomFS: %s: the game's own HeapDef with the mod's texture heap growth in place of the mod's table",
+                   mods_at(base->mod - 1)->name);
     }
     int ok = in && res_heapdef_build(in, n, &out, &out_n);
     free(in);