diff --git a/renderdoc/driver/gl/gl_overlay.cpp b/renderdoc/driver/gl/gl_overlay.cpp
index 0e5fd9ee3..b4eb768de 100644
--- a/renderdoc/driver/gl/gl_overlay.cpp
+++ b/renderdoc/driver/gl/gl_overlay.cpp
@@ -377,7 +377,7 @@ ResourceId GLReplay::RenderOverlay(ResourceId texid, CompType typeHint, DebugOve
       idxs.resize(length);
       gl.glGetBufferSubData(
           eGL_ELEMENT_ARRAY_BUFFER, offset,
-          RDCMIN(GLsizeiptr(length - offset), GLsizeiptr(draw->numIndices * draw->indexByteWidth)),
+          RDCMIN(GLsizeiptr(length - offset), GLsizeiptr(draw->numIndices) * draw->indexByteWidth),
           &idxs[0]);
 
       // unbind the real index buffer
diff --git a/renderdoc/driver/vulkan/vk_postvs.cpp b/renderdoc/driver/vulkan/vk_postvs.cpp
index 2bd753fbc..41d9515aa 100644
--- a/renderdoc/driver/vulkan/vk_postvs.cpp
+++ b/renderdoc/driver/vulkan/vk_postvs.cpp
@@ -1293,13 +1293,13 @@ void VulkanReplay::InitPostVSBuffers(uint32_t eventId)
 
       if(vi->pVertexBindingDescriptions[vb].inputRate == VK_VERTEX_INPUT_RATE_INSTANCE)
       {
-        len = (maxInstance + 1) * vi->pVertexBindingDescriptions[vb].stride;
+        len = uint64_t(maxInstance + 1) * vi->pVertexBindingDescriptions[vb].stride;
 
         offs += drawcall->instanceOffset * vi->pVertexBindingDescriptions[vb].stride;
       }
       else
       {
-        len = (maxIndex + 1) * vi->pVertexBindingDescriptions[vb].stride;
+        len = uint64_t(maxIndex + 1) * vi->pVertexBindingDescriptions[vb].stride;
 
         offs += drawcall->vertexOffset * vi->pVertexBindingDescriptions[vb].stride;
       }