diff --git a/CMakeLists.txt b/CMakeLists.txt
index 10e9082d..7cc3fdab 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -173,10 +173,16 @@ if(BUILD_TESTS)
     list(APPEND UNIT_TESTS_RELATIVE ${_testPath})
   endforeach()
 
+  if(MPI)
+    set(MAX_PES_OPTION MAX_PES 1)
+  else()
+    set(MAX_PES_OPTION "")
+  endif()
+
   add_pfunit_ctest(unitTests
     TEST_SOURCES ${UNIT_TESTS_RELATIVE}
     LINK_LIBRARIES scone
-    MAX_PES 1
+    ${MAX_PES_OPTION}
     )
 
   # pFUnit may have a bug which causes a unused variable `class(Test), allocatable :: t` be