diff --git a/src/imgui/README.md b/src/imgui/README.md
index 1fd52f2fa6..66663b34b3 100644
--- a/src/imgui/README.md
+++ b/src/imgui/README.md
@@ -17,3 +17,6 @@ imstb_truetype.h modification:
 
 Hot fix for open symbolic fonts on windows
 62bdfe6f8d04b88e8bd511cd613be80c0baa7f55
+
+Hot fix for prevent Heap buffer overflow on MAC
+56758dcf8568d91b8a3ad50ccd4b137181ac9490
diff --git a/src/imgui/imstb_truetype.h b/src/imgui/imstb_truetype.h
index 8e4051bd78..86b89d82e6 100644
--- a/src/imgui/imstb_truetype.h
+++ b/src/imgui/imstb_truetype.h
@@ -1664,7 +1664,7 @@ static int stbtt__GetGlyphShapeTT(const stbtt_fontinfo *info, int glyph_index, s
       n = 1+ttUSHORT(endPtsOfContours + numberOfContours*2-2);
 
       m = n + 2*numberOfContours;  // a loose bound on how many vertices we might need
-      vertices = (stbtt_vertex *) STBTT_malloc(m * sizeof(vertices[0]), info->userdata);
+      vertices = (stbtt_vertex *) STBTT_malloc((m + 1) * sizeof(vertices[0]), info->userdata);
       if (vertices == 0)
          return 0;