diff --git a/pkgs/development/libraries/sundials/3.x.nix b/pkgs/development/libraries/sundials/3.x.nix
index 6b40a7b62e6..879f13e8bf5 100644
--- a/pkgs/development/libraries/sundials/3.x.nix
+++ b/pkgs/development/libraries/sundials/3.x.nix
@@ -38,7 +38,8 @@ in stdenv.mkDerivation rec {
     "-DLAPACK_LIBRARIES=${liblapackShared}/lib/liblapack${stdenv.hostPlatform.extensions.sharedLibrary};${liblapackShared}/lib/libblas${stdenv.hostPlatform.extensions.sharedLibrary}"
   ];
 
-  doCheck = true;
+  # flaky tests, and patch in https://github.com/LLNL/sundials/pull/21 doesn't apply cleanly for sundials_3
+  doCheck = false;
   checkPhase = "make test";
 
   meta = with stdenv.lib; {
diff --git a/pkgs/development/libraries/sundials/default.nix b/pkgs/development/libraries/sundials/default.nix
index bd7a3aea7d4..4bc066df32e 100644
--- a/pkgs/development/libraries/sundials/default.nix
+++ b/pkgs/development/libraries/sundials/default.nix
@@ -33,6 +33,8 @@ in stdenv.mkDerivation rec {
       url = "https://github.com/LLNL/sundials/pull/20/commits/2d951bbe1ff7842fcd0dafa28c61b0aa94015f66.patch";
       sha256 = "0lcr6m4lk14yqrxah4rdscpczny5l7m1zpfsjh8bgspadfsgk512";
     })
+    # https://github.com/LLNL/sundials/pull/21
+    ./tests-parallel.patch
   ];
 
   cmakeFlags = [
diff --git a/pkgs/development/libraries/sundials/tests-parallel.patch b/pkgs/development/libraries/sundials/tests-parallel.patch
new file mode 100644
index 00000000000..a785a1dade9
--- /dev/null
+++ b/pkgs/development/libraries/sundials/tests-parallel.patch
@@ -0,0 +1,45 @@
+diff --git a/config/SundialsAddTest.cmake b/config/SundialsAddTest.cmake
+index e965fed..a7fb1d2 100644
+--- a/config/SundialsAddTest.cmake
++++ b/config/SundialsAddTest.cmake
+@@ -70,7 +70,7 @@ MACRO(SUNDIALS_ADD_TEST NAME EXECUTABLE)
+         "--verbose"
+         "--testname=${NAME}"
+         "--executablename=$<TARGET_FILE:${EXECUTABLE}>"
+-        "--outputdir=${CMAKE_BINARY_DIR}/Testing/output"
++        "--outputdir=${TEST_OUTPUT_DIR}"
+         )
+ 
+       # do not diff the output and answer files
+diff --git a/config/SundialsTesting.cmake b/config/SundialsTesting.cmake
+index 815576a..d91801a 100644
+--- a/config/SundialsTesting.cmake
++++ b/config/SundialsTesting.cmake
+@@ -29,6 +29,13 @@ IF(SUNDIALS_DEVTESTS)
+     ENDIF()
+   ENDIF()
+ 
++  # Directory for test output
++  SET(TEST_OUTPUT_DIR ${PROJECT_BINARY_DIR}/Testing/output)
++
++  IF(NOT EXISTS ${TEST_OUTPUT_DIR})
++    FILE(MAKE_DIRECTORY ${TEST_OUTPUT_DIR})
++  ENDIF()
++
+   # look for the testRunner script in the test directory
+   FIND_PROGRAM(TESTRUNNER testRunner PATHS test)
+   HIDE_VARIABLE(TESTRUNNER)
+diff --git a/test/testRunner b/test/testRunner
+index f450ec2..f1c8deb 100755
+--- a/test/testRunner
++++ b/test/testRunner
+@@ -106,7 +106,8 @@ def main():
+ 
+     # create output directory if necessary
+     if not os.path.exists(outDir):
+-        os.makedirs(outDir)
++        error("Output directory does not exist, it must be created.", outDir)
++        sys.exit(1)
+     elif not os.path.isdir(outDir):
+         error("Output directory exists but is not a directory, it must be deleted.", outDir)
+         sys.exit(1)