diff --git a/integration-test/src/test/scala/RunnerTest.scala b/integration-test/src/test/scala/RunnerTest.scala
index d810f9475..d3dc0c580 100755
--- a/integration-test/src/test/scala/RunnerTest.scala
+++ b/integration-test/src/test/scala/RunnerTest.scala
@@ -95,12 +95,41 @@ object SbtRunnerTest extends SimpleTestSuite with PowerAssertions {
   }
 
   test("sbt with -Xms2048M -Xmx2048M -Xss6M in SBT_OPTS") {
-    if (isWindows) cancel("Test not supported on windows")
     val out = sbtProcessWithOpts("compile -v", "", "-Xms2048M -Xmx2048M -Xss6M").!!.linesIterator.toList
     assert(out.contains[String]("-Xss6M"))
     ()
   }
 
+  test("sbt with -Dhttp.proxyHost=proxy -Dhttp.proxyPort=8080 in SBT_OPTS") {
+    val out = sbtProcessWithOpts("compile -v", "", "-Dhttp.proxyHost=proxy -Dhttp.proxyPort=8080").!!.linesIterator.toList
+    assert(out.contains[String]("-Dhttp.proxyHost=proxy"))
+    assert(out.contains[String]("-Dhttp.proxyPort=8080"))
+    ()
+  }
+
+  test("sbt with -XX:ParallelGCThreads=16 -XX:PermSize=128M in SBT_OPTS") {
+    val out = sbtProcessWithOpts("compile -v", "", "-XX:ParallelGCThreads=16 -XX:PermSize=128M").!!.linesIterator.toList
+    assert(out.contains[String]("-XX:ParallelGCThreads=16"))
+    assert(out.contains[String]("-XX:PermSize=128M"))
+    ()
+  }
+
+  test("sbt with -XX:+UseG1GC -XX:+PrintGC in SBT_OPTS") {
+    val out = sbtProcessWithOpts("compile -v", "", "-XX:+UseG1GC -XX:+PrintGC").!!.linesIterator.toList
+    assert(out.contains[String]("-XX:+UseG1GC"))
+    assert(out.contains[String]("-XX:+PrintGC"))
+    assert(!out.contains[String]("-XX:+UseG1GC=-XX:+PrintGC"))
+    ()
+  }
+
+  test("sbt with -XX:-UseG1GC -XX:-PrintGC in SBT_OPTS") {
+    val out = sbtProcessWithOpts("compile -v", "", "-XX:-UseG1GC -XX:-PrintGC").!!.linesIterator.toList
+    assert(out.contains[String]("-XX:-UseG1GC"))
+    assert(out.contains[String]("-XX:-PrintGC"))
+    assert(!out.contains[String]("-XX:-UseG1GC=-XX:-PrintGC"))
+    ()
+  }
+
   test("sbt with --no-colors in SBT_OPTS") {
     if (isWindows) cancel("Test not supported on windows")
     val out = sbtProcessWithOpts("compile -v", "", "--no-colors").!!.linesIterator.toList
diff --git a/src/universal/bin/sbt.bat b/src/universal/bin/sbt.bat
index 577a2adac..417b79ad3 100755
--- a/src/universal/bin/sbt.bat
+++ b/src/universal/bin/sbt.bat
@@ -49,7 +49,11 @@ rem users can set SBT_OPTS via .sbtopts
 if exist .sbtopts for /F %%A in (.sbtopts) do (
   set _sbtopts_line=%%A
   if not "!_sbtopts_line:~0,1!" == "#" (
-    set _SBT_OPTS=%%A %SBT_OPTS%
+    if defined _SBT_OPTS (
+      set _SBT_OPTS=!_SBT_OPTS! %%A
+    ) else (
+      set _SBT_OPTS=%%A
+    )
   )
 )
 
@@ -404,21 +408,45 @@ if "%~0" == "new" (
 
 if "%g:~0,2%" == "-D" (
   rem special handling for -D since '=' gets parsed away
-  echo "%g%" | find "=" > null
-  if ERRORLEVEL 1 (
-    if not "%~1" == "" (
-      call :dlog [args_loop] -D argument %~0=%~1
-      set "SBT_ARGS=!SBT_ARGS! %~0=%~1"
-      shift
-      goto args_loop
+  for /F "tokens=1 delims==" %%a in ("%g%") do (
+    rem make sure it doesn't have the '=' already
+    if "%g%" == "%%a" (
+      if not "%~1" == "" (
+        call :dlog [args_loop] -D argument %~0=%~1
+        set "SBT_ARGS=!SBT_ARGS! %~0=%~1"
+        shift
+        goto args_loop
+      ) else (
+        echo %g% is missing a value
+        goto error
+      )
     ) else (
-      echo %g% is missing a value
-      goto error
+      call :dlog [args_loop] -D argument %~0
+      set "SBT_ARGS=!SBT_ARGS! %~0"
+      goto args_loop
+    )
+  )
+)
+
+if not "%g:~0,5%" == "-XX:+" if not "%g:~0,5%" == "-XX:-" if "%g:~0,3%" == "-XX" (
+  rem special handling for -XX since '=' gets parsed away
+  for /F "tokens=1 delims==" %%a in ("%g%") do (
+    rem make sure it doesn't have the '=' already
+    if "%g%" == "%%a" (
+      if not "%~1" == "" (
+        call :dlog [args_loop] -XX argument %~0=%~1
+        set "SBT_ARGS=!SBT_ARGS! %~0=%~1"
+        shift
+        goto args_loop
+      ) else (
+        echo %g% is missing a value
+        goto error
+      )
+    ) else (
+      call :dlog [args_loop] -XX argument %~0
+      set "SBT_ARGS=!SBT_ARGS! %~0"
+      goto args_loop
     )
-  ) else (
-    call :dlog [args_loop] -D argument %~0
-    set "SBT_ARGS=!SBT_ARGS! %~0"
-    goto args_loop
   )
 )
 
@@ -584,16 +612,28 @@ shift
 if [%0] EQU [] goto echolist_end
 set "p=%0"
 
-rem special handling for -D since '=' gets parsed away
 if "%p:~0,2%" == "-D" (
- rem if "-Dscala.ext.dirs" (replace all = with nothing) == "-Dscala.ext.dirs"
- rem (e.g. verify it doesn't have the = already)
+  rem special handling for -D since '=' gets parsed away
+  for /F "tokens=1 delims==" %%a in ("%p%") do (
+    rem make sure it doesn't have the '=' already
+    if "%p%" == "%%a" if not "%~1" == "" (
+      echo %0=%1
+      shift
+      goto echolist
+    )
+  )
+)
 
- if "x%p:^==%" == "x%p%" if not "%~1" == "" (
-     echo %0=%1
-     shift
-     goto echolist
- )
+if not "%p:~0,5%" == "-XX:+" if not "%p:~0,5%" == "-XX:-" if "%p:~0,3%" == "-XX" (
+  rem special handling for -XX since '=' gets parsed away
+  for /F "tokens=1 delims==" %%a in ("%p%") do (
+    rem make sure it doesn't have the '=' already
+    if "%p%" == "%%a" if not "%~1" == "" (
+      echo %0=%1
+      shift
+      goto echolist
+    )
+  )
 )
 
 echo %0
@@ -613,24 +653,33 @@ exit /B 0
 
   rem evict memory related options
   set _new_java_opts=
-
-  for /F %%g in ("!_JAVA_OPTS!") do (
+  set _old_java_opts=!_JAVA_OPTS!
+:next_java_opt
+  if "!_old_java_opts!" == "" goto :done_java_opt
+  for /F "tokens=1,*" %%g in ("!_old_java_opts!") do (
     set "p=%%g"
     if not "!p:~0,4!" == "-Xmx" if not "!p:~0,4!" == "-Xms" if not "!p:~0,15!" == "-XX:MaxPermSize" if not "!p:~0,20!" == "-XX:MaxMetaspaceSize" if not "!p:~0,25!" == "-XX:ReservedCodeCacheSize" (
       set _new_java_opts=!_new_java_opts! %%g
     )
+    set "_old_java_opts=%%h"
   )
+  goto :next_java_opt
+:done_java_opt
   set _JAVA_OPTS=!_new_java_opts!
 
   set _new_sbt_opts=
-
-  for /F %%g in ("!_SBT_OPTS!") do (
+  set _old_sbt_opts=!_SBT_OPTS!
+:next_sbt_opt
+  if "!_old_sbt_opts!" == "" goto :done_sbt_opt
+  for /F "tokens=1,*" %%g in ("!_old_sbt_opts!") do (
     set "p=%%g"
     if not "!p:~0,4!" == "-Xmx" if not "!p:~0,4!" == "-Xms" if not "!p:~0,15!" == "-XX:MaxPermSize" if not "!p:~0,20!" == "-XX:MaxMetaspaceSize" if not "!p:~0,25!" == "-XX:ReservedCodeCacheSize" (
       set _new_sbt_opts=!_new_sbt_opts! %%g
     )
+    set "_old_sbt_opts=%%h"
   )
-
+  goto :next_sbt_opt
+:done_sbt_opt
   set _SBT_OPTS=!_new_sbt_opts!
 
   rem a ham-fisted attempt to move some memory settings in concert