diff --git a/src/worksp-vc70/libmzsch/libmzsch.vcproj b/src/worksp-vc70/libmzsch/libmzsch.vcproj
index 8e488cba01..96951bdd95 100644
--- a/src/worksp-vc70/libmzsch/libmzsch.vcproj
+++ b/src/worksp-vc70/libmzsch/libmzsch.vcproj
@@ -69,6 +69,7 @@
                         CharacterSet="2">
                         <Tool
                                 Name="VCCLCompilerTool"
+				AdditionalOptions="/Oy-"
                                 GlobalOptimizations="TRUE"
                                 InlineFunctionExpansion="2"
                                 EnableIntrinsicFunctions="TRUE"
diff --git a/src/worksp/libmzsch/libmzsch.vcproj b/src/worksp/libmzsch/libmzsch.vcproj
index 00fb52f4bd..7f08973b4e 100644
--- a/src/worksp/libmzsch/libmzsch.vcproj
+++ b/src/worksp/libmzsch/libmzsch.vcproj
@@ -75,6 +75,7 @@
 			CharacterSet="2">
 			<Tool
 				Name="VCCLCompilerTool"
+				AdditionalOptions="/Oy-"
 				GlobalOptimizations="TRUE"
 				InlineFunctionExpansion="2"
 				EnableIntrinsicFunctions="TRUE"