diff --git a/VersionASM b/VersionASM
index 537ca4727ca379d0ee2a62c314bc13682b579d7e..40adfef5e58b33d8ecdbb70a131e9ae4f3200ade 100644
--- a/VersionASM
+++ b/VersionASM
@@ -11,13 +11,13 @@
                         GBLS    Module_HelpVersion
                         GBLS    Module_ComponentName
                         GBLS    Module_ComponentPath
-Module_MajorVersion     SETS    "5.09"
-Module_Version          SETA    509
+Module_MajorVersion     SETS    "5.10"
+Module_Version          SETA    510
 Module_MinorVersion     SETS    ""
-Module_Date             SETS    "26 Nov 2010"
-Module_ApplicationDate  SETS    "26-Nov-10"
+Module_Date             SETS    "04 Dec 2010"
+Module_ApplicationDate  SETS    "04-Dec-10"
 Module_ComponentName    SETS    "Wimp"
 Module_ComponentPath    SETS    "castle/RiscOS/Sources/Desktop/Wimp"
-Module_FullVersion      SETS    "5.09"
-Module_HelpVersion      SETS    "5.09 (26 Nov 2010)"
+Module_FullVersion      SETS    "5.10"
+Module_HelpVersion      SETS    "5.10 (04 Dec 2010)"
                         END
diff --git a/VersionNum b/VersionNum
index c7d5cab0f174bed6580e835fa6c6780410bfa845..5be7979ac473a49ac7a21d791cc39f2c630ea225 100644
--- a/VersionNum
+++ b/VersionNum
@@ -1,23 +1,23 @@
-/* (5.09)
+/* (5.10)
  *
  * This file is automatically maintained by srccommit, do not edit manually.
  * Last processed by srccommit version: 1.1.
  *
  */
-#define Module_MajorVersion_CMHG        5.09
+#define Module_MajorVersion_CMHG        5.10
 #define Module_MinorVersion_CMHG        
-#define Module_Date_CMHG                26 Nov 2010
+#define Module_Date_CMHG                04 Dec 2010
 
-#define Module_MajorVersion             "5.09"
-#define Module_Version                  509
+#define Module_MajorVersion             "5.10"
+#define Module_Version                  510
 #define Module_MinorVersion             ""
-#define Module_Date                     "26 Nov 2010"
+#define Module_Date                     "04 Dec 2010"
 
-#define Module_ApplicationDate          "26-Nov-10"
+#define Module_ApplicationDate          "04-Dec-10"
 
 #define Module_ComponentName            "Wimp"
 #define Module_ComponentPath            "castle/RiscOS/Sources/Desktop/Wimp"
 
-#define Module_FullVersion              "5.09"
-#define Module_HelpVersion              "5.09 (26 Nov 2010)"
-#define Module_LibraryVersionInfo       "5:9"
+#define Module_FullVersion              "5.10"
+#define Module_HelpVersion              "5.10 (04 Dec 2010)"
+#define Module_LibraryVersionInfo       "5:10"
diff --git a/s/Wimp04 b/s/Wimp04
index afd1ff75b25864844961127c9a7a5c10df9f1d4f..628bc2a9f8f70c35f687b36f36f227ddc9493576 100644
--- a/s/Wimp04
+++ b/s/Wimp04
@@ -5825,6 +5825,8 @@ checkhandle
 ; Check the window structure for being inside valid memory
 ;
         Abs     handle,handle
+        TST     handle,#3
+        BNE     errhandle ; If it's not word aligned, it's definitely invalid
         MOV     R0,handle
         ADD     R1,R0,#w_size
         Debug   valid,"WIMP validating: ",r0,r1