diff --git a/imgui.cpp b/imgui.cpp
index 8b3f900e..eac6a26b 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -6580,16 +6580,15 @@ void ImGui::PlotEx(ImGuiPlotType plot_type, const char* label, float (*values_ge
 
     RenderFrame(frame_bb.Min, frame_bb.Max, window->Color(ImGuiCol_FrameBg), true, style.FrameRounding);
 
-    int res_w = ImMin((int)graph_size.x, values_count);
-    if (plot_type == ImGuiPlotType_Lines)
-        res_w -= 1;
+    int res_w = ImMin((int)graph_size.x, values_count) + ((plot_type == ImGuiPlotType_Lines) ? -1 : 0);
+    int item_count = values_count + ((plot_type == ImGuiPlotType_Lines) ? -1 : 0);
 
     // Tooltip on hover
     int v_hovered = -1;
     if (IsHovered(inner_bb, 0))
     {
         const float t = ImClamp((g.IO.MousePos.x - inner_bb.Min.x) / (inner_bb.Max.x - inner_bb.Min.x), 0.0f, 0.9999f);
-        const int v_idx = (int)(t * (values_count + ((plot_type == ImGuiPlotType_Lines) ? -1 : 0)));
+        const int v_idx = (int)(t * item_count);
         IM_ASSERT(v_idx >= 0 && v_idx < values_count);
 
         const float v0 = values_getter(data, (v_idx + values_offset) % values_count);
@@ -6613,7 +6612,7 @@ void ImGui::PlotEx(ImGuiPlotType plot_type, const char* label, float (*values_ge
     for (int n = 0; n < res_w; n++)
     {
         const float t1 = t0 + t_step;
-        const int v_idx = (int)(t0 * values_count + 0.5f);
+        const int v_idx = (int)(t0 * item_count + 0.5f);
         IM_ASSERT(v_idx >= 0 && v_idx < values_count);
         const float v1 = values_getter(data, (v_idx + values_offset + 1) % values_count);
         const ImVec2 p1 = ImVec2( t1, 1.0f - ImSaturate((v1 - scale_min) / (scale_max - scale_min)) );