diff --git a/README.md b/README.md
index 60e6c98..aa2ec16 100644
--- a/README.md
+++ b/README.md
@@ -48,6 +48,10 @@ Usage:
       --pbr-specular-glossiness
                                 (WIP) Experimentally fill in the
                                 KHR_materials_pbrSpecularGlossiness extension.
+      --blend-shape-normals     Include blend shape normals, if reported
+                                present by the FBX SDK.
+      --blend-shape-tangents    Include blend shape tangents, if reported
+                                present by the FBX SDK.
   -k, --keep-attribute arg      Used repeatedly to build a limiting set of
                                 vertex attributes to keep.
   -v, --verbose                 Enable verbose output.
@@ -81,6 +85,13 @@ Some of these switches are not obvious:
   the conversion process. This is a way to trim the size of the resulting glTF
   if you know the FBX contains superfluous attributes. The supported arguments
   are `position`, `normal`, `tangent`, `color`, `uv0`, and `uv1`.
+- When **blend shapes** are present, you may use `--blend-shape-normals` and
+  `--blend-shape-tangents` to include normal and tangent attributes in the glTF
+  morph targets. They are not included by default because they rarely or never
+  seem to be correctly present in the actual FBX source, which means the SDK
+  must be computing them from geometry, unasked? In any case, they are beyond
+  the control of the artist, and can yield strange crinkly behaviour. Since
+  they also take up significant space in the output file, we made them opt-in.
 
 ## Building it on your own
 
diff --git a/src/Raw2Gltf.cpp b/src/Raw2Gltf.cpp
index 2c06466..9ed143e 100644
--- a/src/Raw2Gltf.cpp
+++ b/src/Raw2Gltf.cpp
@@ -619,10 +619,10 @@ ModelData *Raw2Gltf(
                         auto blendVertex = surfaceModel.GetVertex(jj).blends[channelIx];
                         shapeBounds.AddPoint(blendVertex.position);
                         positions.push_back(blendVertex.position);
-                        if (channel.hasNormals) {
+                        if (options.useBlendShapeTangents && channel.hasNormals) {
                             normals.push_back(blendVertex.normal);
                         }
-                        if (channel.hasTangents) {
+                        if (options.useBlendShapeTangents && channel.hasTangents) {
                             tangents.push_back(blendVertex.tangent);
                         }
                     }
@@ -633,14 +633,14 @@ ModelData *Raw2Gltf(
                     pAcc->max = toStdVec(shapeBounds.max);
 
                     std::shared_ptr<AccessorData> nAcc;
-                    if (channel.hasNormals) {
+                    if (!normals.empty()) {
                         nAcc = gltf->AddAccessorWithView(
                             *gltf->GetAlignedBufferView(buffer, BufferViewData::GL_ARRAY_BUFFER),
                             GLT_VEC3F, normals);
                     }
 
                     std::shared_ptr<AccessorData> tAcc;
-                    if (channel.hasTangents) {
+                    if (!tangents.empty()) {
                         nAcc = gltf->AddAccessorWithView(
                             *gltf->GetAlignedBufferView(buffer, BufferViewData::GL_ARRAY_BUFFER),
                             GLT_VEC4F, tangents);
diff --git a/src/Raw2Gltf.h b/src/Raw2Gltf.h
index 5de9218..8e6ecf5 100644
--- a/src/Raw2Gltf.h
+++ b/src/Raw2Gltf.h
@@ -53,6 +53,10 @@ struct GltfOptions
     bool usePBRMetRough;
     /** Whether to use KHR_materials_pbrSpecularGlossiness to extend material definitions. */
     bool usePBRSpecGloss;
+    /** Whether to include blend shape normals, if present according to the SDK. */
+    bool useBlendShapeNormals;
+    /** Whether to include blend shape tangents, if present according to the SDK. */
+    bool useBlendShapeTangents;
 };
 
 struct ComponentType {
diff --git a/src/main.cpp b/src/main.cpp
index 0fcd6bc..faa6c2d 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -44,12 +44,14 @@ int main(int argc, char *argv[])
 
     GltfOptions gltfOptions{
         -1,            // keepAttribs
-        false,        // outputBinary
-        false,        // embedResources
-        false,        // useDraco
-        false,        // useKHRMatCom
-        false,        // usePBRMetRough
-        false        // usePBRSpecGloss
+        false,         // outputBinary
+        false,         // embedResources
+        false,         // useDraco
+        false,         // useKHRMatCom
+        false,         // usePBRMetRough
+        false,         // usePBRSpecGloss
+        false,         // useBlendShapeNormals
+        false,         // useBlendShapeTangents
     };
 
     options.positional_help("[<FBX File>]");
@@ -81,6 +83,12 @@ int main(int argc, char *argv[])
                (
                    "pbr-specular-glossiness", "(WIP) Experimentally fill in the KHR_materials_pbrSpecularGlossiness extension.",
                    cxxopts::value<bool>(gltfOptions.usePBRSpecGloss))
+               (
+                   "blend-shape-normals", "Include blend shape normals, if reported present by the FBX SDK.",
+                   cxxopts::value<bool>(gltfOptions.useBlendShapeNormals))
+               (
+                   "blend-shape-tangents", "Include blend shape tangents, if reported present by the FBX SDK.",
+                   cxxopts::value<bool>(gltfOptions.useBlendShapeTangents))
                (
                    "k,keep-attribute", "Used repeatedly to build a limiting set of vertex attributes to keep.",
                    cxxopts::value<std::vector<std::string>>())