diff --git a/pkgs/development/libraries/db4/cygwin.patch b/pkgs/development/libraries/db4/cygwin-4.4.patch
similarity index 100%
rename from pkgs/development/libraries/db4/cygwin.patch
rename to pkgs/development/libraries/db4/cygwin-4.4.patch
diff --git a/pkgs/development/libraries/db4/cygwin-4.5.patch b/pkgs/development/libraries/db4/cygwin-4.5.patch
new file mode 100644
index 000000000000..410106722a6c
--- /dev/null
+++ b/pkgs/development/libraries/db4/cygwin-4.5.patch
@@ -0,0 +1,22 @@
+diff -rc db-4.5.20-orig/os/os_flock.c db-4.5.20/os/os_flock.c
+*** db-4.5.20-orig/os/os_flock.c	2006-10-13 12:36:12.000000000 +0200
+--- db-4.5.20/os/os_flock.c	2006-10-13 12:40:11.000000000 +0200
+***************
+*** 30,35 ****
+--- 30,44 ----
+  
+  	DB_ASSERT(dbenv, F_ISSET(fhp, DB_FH_OPENED) && fhp->fd != -1);
+  
++ #ifdef __CYGWIN__
++ 	/*
++ 	 * Windows file locking interferes with read/write operations, so we
++ 	 * map the ranges to an area past the end of the file.
++ 	 */
++ 	DB_ASSERT(offset < (off_t) 1 << 62);
++ 	offset += (off_t) 1 << 62;
++ #endif
++ 
+  	fl.l_start = offset;
+  	fl.l_len = 1;
+  	fl.l_type = acquire ? F_WRLCK : F_UNLCK;
+Only in db-4.5.20/os: os_flock.c~
diff --git a/pkgs/development/libraries/db4/default.nix b/pkgs/development/libraries/db4/db4-4.4.nix
similarity index 95%
rename from pkgs/development/libraries/db4/default.nix
rename to pkgs/development/libraries/db4/db4-4.4.nix
index 2b4246ff4615..f17cc0ae24fa 100644
--- a/pkgs/development/libraries/db4/default.nix
+++ b/pkgs/development/libraries/db4/db4-4.4.nix
@@ -11,4 +11,4 @@ stdenv.mkDerivation ({
     (if cxxSupport then "--enable-cxx" else "--disable-cxx")
     (if cxxSupport then "--enable-compat185" else "--disable-compat185")
   ];
-} // (if stdenv.system == "i686-cygwin" then {patches = [./cygwin.patch];} else {}))
+} // (if stdenv.system == "i686-cygwin" then {patches = [./cygwin-4.4.patch];} else {}))
diff --git a/pkgs/development/libraries/db4/db4-4.5.20.nix b/pkgs/development/libraries/db4/db4-4.5.nix
similarity index 78%
rename from pkgs/development/libraries/db4/db4-4.5.20.nix
rename to pkgs/development/libraries/db4/db4-4.5.nix
index 5c20b2f451ff..9134c7f483b4 100644
--- a/pkgs/development/libraries/db4/db4-4.5.20.nix
+++ b/pkgs/development/libraries/db4/db4-4.5.nix
@@ -1,6 +1,6 @@
 {stdenv, fetchurl, cxxSupport ? true, compat185 ? true}:
 
-stdenv.mkDerivation ({
+stdenv.mkDerivation {
   name = "db4-4.5.20";
   builder = ./builder.sh;
   src = fetchurl {
@@ -11,4 +11,5 @@ stdenv.mkDerivation ({
     (if cxxSupport then "--enable-cxx" else "--disable-cxx")
     (if cxxSupport then "--enable-compat185" else "--disable-compat185")
   ];
-} // (if stdenv.system == "i686-cygwin" then {patches = [./cygwin.patch];} else {}))
+  patches = [./cygwin-4.5.patch];
+}
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 385cfe8758dc..4ccad265e5c9 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -1076,7 +1076,13 @@ rec {
     inherit fetchurl stdenv;
   };
 
-  db4 = (import ../development/libraries/db4) {
+  db4 = db44;
+
+  db44 = import ../development/libraries/db4/db4-4.4.nix {
+    inherit fetchurl stdenv;
+  };
+
+  db45 = import ../development/libraries/db4/db4-4.5.nix {
     inherit fetchurl stdenv;
   };
 
@@ -2773,7 +2779,8 @@ rec {
   };
 
   nix = (import ../misc/nix) {
-    inherit fetchurl stdenv aterm db4 perl curl bzip2;
+    inherit fetchurl stdenv aterm perl curl bzip2;
+    db4 = db44;
   };
 
   nixUnstable = nix;