diff --git a/ANNOUNCE b/ANNOUNCE
index 40b49f7f1..329a3f0f2 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -548,6 +548,8 @@ Version 1.6.0beta31 [October 27, 2012]
     depends on it; this obliges people who set it to consider whether they
     really want it off if they happen to use any of the interfaces in
     question (typically most users who disable it won't).
+  Fixed GUIDs in projects/vstudio. Some were duplicated or missing,
+    resulting in VS2010 having to update the files.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index ffa2caceb..b38a2ca61 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4300,6 +4300,8 @@ Version 1.6.0beta31 [October 27, 2012]
     depends on it; this obliges people who set it to consider whether they
     really want it off if they happen to use any of the interfaces in
     question (typically most users who disable it won't).
+  Fixed GUIDs in projects/vstudio. Some were duplicated or missing,
+    resulting in VS2010 having to update the files.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/projects/vstudio/pngstest/pngstest.vcxproj b/projects/vstudio/pngstest/pngstest.vcxproj
index efd74e255..fc2e9d5d8 100644
--- a/projects/vstudio/pngstest/pngstest.vcxproj
+++ b/projects/vstudio/pngstest/pngstest.vcxproj
@@ -19,7 +19,7 @@
     </ProjectConfiguration>
   </ItemGroup>
   <PropertyGroup Label="Globals">
-    <ProjectGuid>{9B36B6FE-7FC0-434F-A71F-BBEF8099F1D8}</ProjectGuid>
+    <ProjectGuid>{277AC57F-313B-4D06-B119-A3CDB672D2FF}</ProjectGuid>
     <Keyword>Win32Proj</Keyword>
     <RootNamespace>pngstest</RootNamespace>
   </PropertyGroup>
diff --git a/projects/vstudio/pngunknown/pngunknown.vcxproj b/projects/vstudio/pngunknown/pngunknown.vcxproj
index 1f1780a8e..6f9059544 100644
--- a/projects/vstudio/pngunknown/pngunknown.vcxproj
+++ b/projects/vstudio/pngunknown/pngunknown.vcxproj
@@ -19,7 +19,7 @@
     </ProjectConfiguration>
   </ItemGroup>
   <PropertyGroup Label="Globals">
-    <ProjectGuid>{9B36B6FE-7FC0-434F-A71F-BBEF8099F1D8}</ProjectGuid>
+    <ProjectGuid>{C5D3156C-8C8C-4936-B35F-2B829BA36FEC}</ProjectGuid>
     <Keyword>Win32Proj</Keyword>
     <RootNamespace>pngunknown</RootNamespace>
   </PropertyGroup>
diff --git a/projects/vstudio/zlib/zlib.vcxproj b/projects/vstudio/zlib/zlib.vcxproj
index d56721d1c..8e271988f 100644
--- a/projects/vstudio/zlib/zlib.vcxproj
+++ b/projects/vstudio/zlib/zlib.vcxproj
@@ -32,7 +32,9 @@
     <ClCompile Include="$(ZLibSrcDir)\zutil.c" />
   </ItemGroup>
   <PropertyGroup Label="Globals">
+    <ProjectGuid>{60F89955-91C6-3A36-8000-13C592FEC2DF}</ProjectGuid>
     <Keyword>Win32Proj</Keyword>
+    <RootNamespace>zlib</RootNamespace>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
   <Import Project="$(SolutionDir)\zlib.props" />