diff --git a/EdkCompatibilityPkg/Foundation/Library/Pei/PeiLib/Decompress.c b/EdkCompatibilityPkg/Foundation/Library/Pei/PeiLib/Decompress.c
index 43446a37dd..d35d946d63 100644
--- a/EdkCompatibilityPkg/Foundation/Library/Pei/PeiLib/Decompress.c
+++ b/EdkCompatibilityPkg/Foundation/Library/Pei/PeiLib/Decompress.c
@@ -337,7 +337,8 @@ Returns:
   }
 
   while (Index <= 16) {
-    Weight[Index++] = (UINT16) (1U << (16 - Index));
+    Weight[Index] = (UINT16) (1U << (16 - Index));
+    Index++;
   }
 
   Index = (UINT16) (Start[TableBits + 1] >> JuBits);