diff --git a/libs/vkd3d-shader/ir.c b/libs/vkd3d-shader/ir.c
index 66cbfe1f..8fd8a742 100644
--- a/libs/vkd3d-shader/ir.c
+++ b/libs/vkd3d-shader/ir.c
@@ -8054,7 +8054,7 @@ static void vsir_validate_signature_element(struct validation_context *ctx,
     enum vkd3d_tessellator_domain expected_tess_domain = VKD3D_TESSELLATOR_DOMAIN_INVALID;
     const char *signature_type_name = signature_type_names[signature_type];
     const struct signature_element *element = &signature->elements[idx];
-    bool integer_type = false, is_outer = false;
+    bool integer_type = false, is_outer = false, is_gs_output;
     unsigned int semantic_index_max = 0;
 
     if (element->register_count == 0)
@@ -8067,6 +8067,13 @@ static void vsir_validate_signature_element(struct validation_context *ctx,
                 "element %u of %s signature: Invalid register index %u and count %u.",
                 idx, signature_type_name, element->register_index, element->register_count);
 
+    is_gs_output = ctx->program->shader_version.type == VKD3D_SHADER_TYPE_GEOMETRY
+            && signature_type == SIGNATURE_TYPE_OUTPUT;
+    if (element->stream_index >= VKD3D_MAX_STREAM_COUNT || (element->stream_index != 0 && !is_gs_output))
+        validator_error(ctx, VKD3D_SHADER_ERROR_VSIR_INVALID_SIGNATURE,
+                "element %u of %s signature: Invalid stream index %u.",
+                idx, signature_type_name, element->stream_index);
+
     if (element->mask == 0 || (element->mask & ~0xf))
         validator_error(ctx, VKD3D_SHADER_ERROR_VSIR_INVALID_SIGNATURE,
                 "element %u of %s signature: Invalid mask %#x.", idx, signature_type_name, element->mask);
diff --git a/libs/vkd3d-shader/vkd3d_shader_private.h b/libs/vkd3d-shader/vkd3d_shader_private.h
index c25c0041..75c8430a 100644
--- a/libs/vkd3d-shader/vkd3d_shader_private.h
+++ b/libs/vkd3d-shader/vkd3d_shader_private.h
@@ -62,6 +62,8 @@
 #define VKD3D_SHADER_COMPONENT_TYPE_COUNT (VKD3D_SHADER_COMPONENT_UINT64 + 1)
 #define VKD3D_SHADER_MINIMUM_PRECISION_COUNT (VKD3D_SHADER_MINIMUM_PRECISION_UINT_16 + 1)
 
+#define VKD3D_MAX_STREAM_COUNT 4
+
 enum vkd3d_shader_error
 {
     VKD3D_SHADER_ERROR_DXBC_INVALID_SIZE                = 1,