diff --git a/src/libslic3r/TextureDisplacement.cpp b/src/libslic3r/TextureDisplacement.cpp
index ab63a75c70..26e8726a72 100644
--- a/src/libslic3r/TextureDisplacement.cpp
+++ b/src/libslic3r/TextureDisplacement.cpp
@@ -283,7 +283,7 @@ bool height_texture_has_color(const TextureDisplacementLayer &layer)
     return decode_height_texture(layer).has_color();
 }
 
-DecodedHeightTexture decode_height_texture(const TextureDisplacementLayer &layer)
+DecodedHeightTexture decode_height_texture(const TextureDisplacementLayer &layer, bool keep_decoded)
 {
     DecodedHeightTexture result;
     if (layer.empty())
@@ -351,13 +351,15 @@ DecodedHeightTexture decode_height_texture(const TextureDisplacementLayer &layer
                 }
         }
 
-        std::lock_guard<std::mutex> lock(g_decoded_texture_cache.mutex);
-        // Opportunistically drop entries for image_data that no longer exists anywhere, so the
-        // cache doesn't grow without bound across many add/remove-texture cycles in a long session.
-        auto &entries = g_decoded_texture_cache.entries;
-        for (auto it = entries.begin(); it != entries.end();)
-            it = it->second.first.expired() ? entries.erase(it) : std::next(it);
-        entries[key] = { std::weak_ptr<const std::vector<unsigned char>>(layer.image_data), result };
+        if (keep_decoded) {
+            std::lock_guard<std::mutex> lock(g_decoded_texture_cache.mutex);
+            // Opportunistically drop entries for image_data that no longer exists anywhere, so the
+            // cache doesn't grow without bound across many add/remove-texture cycles in a long session.
+            auto &entries = g_decoded_texture_cache.entries;
+            for (auto it = entries.begin(); it != entries.end();)
+                it = it->second.first.expired() ? entries.erase(it) : std::next(it);
+            entries[key] = { std::weak_ptr<const std::vector<unsigned char>>(layer.image_data), result };
+        }
     }
 
     // The image-adjustment panel's live edits, on top of the decode and before the smoothing. Before,
diff --git a/src/libslic3r/TextureDisplacement.hpp b/src/libslic3r/TextureDisplacement.hpp
index 6bd5d1ea33..919dfad654 100644
--- a/src/libslic3r/TextureDisplacement.hpp
+++ b/src/libslic3r/TextureDisplacement.hpp
@@ -599,8 +599,9 @@ DecodedHeightTexture downscale_height_texture(const DecodedHeightTexture &src, i
 // colour PNGs are accepted; for a colour source the height is its luminance, using the same
 // coefficients wxImage::ConvertToGreyscale() uses, so a texture imported as colour displaces exactly
 // as it did when the importer flattened it to grey on the way in. Returns an empty
-// DecodedHeightTexture if image_data is empty or is not a PNG at all.
-DecodedHeightTexture decode_height_texture(const TextureDisplacementLayer &layer);
+// DecodedHeightTexture if image_data is empty or is not a PNG at all. keep_decoded = false leaves the
+// result out of the decode cache, for one-off reads such as a picker thumbnail that must not hold full-size pixels.
+DecodedHeightTexture decode_height_texture(const TextureDisplacementLayer &layer, bool keep_decoded = true);
 
 // decode_height_texture(layer).has_color(), answered from the decode cache rather than from a copy of the
 // texture - cheap enough to ask every frame. Smoothing does not change it, so the raw decode is what is read.
diff --git a/src/slic3r/GUI/Gizmos/GLGizmoTextureDisplacement.cpp b/src/slic3r/GUI/Gizmos/GLGizmoTextureDisplacement.cpp
index be1f72e520..646a23912a 100644
--- a/src/slic3r/GUI/Gizmos/GLGizmoTextureDisplacement.cpp
+++ b/src/slic3r/GUI/Gizmos/GLGizmoTextureDisplacement.cpp
@@ -4122,7 +4122,7 @@ const GLGizmoTextureDisplacement::LibraryTexture *GLGizmoTextureDisplacement::ge
     if (entry.image_data) {
         TextureDisplacementLayer probe;
         probe.image_data = entry.image_data;
-        entry.thumbnail  = upload_height_thumbnail(decode_height_texture(probe));
+        entry.thumbnail  = upload_height_thumbnail(decode_height_texture(probe, /* keep_decoded */ false));
         if (!entry.thumbnail)
             entry.image_data.reset(); // decoded to nothing usable - treat it as a failed load
     } else {