diff --git a/zorg/buildbot/builders/OpenMPBuilder.py b/zorg/buildbot/builders/OpenMPBuilder.py
--- a/zorg/buildbot/builders/OpenMPBuilder.py
+++ b/zorg/buildbot/builders/OpenMPBuilder.py
@@ -133,6 +133,16 @@
     if add_lit_checks != None:
         for add_check in add_lit_checks:
             ninja_test_args = ['ninja', WithProperties('-j %s' % jobs)]
+            # Limit the number of threads to use for GPU libc to prevent errors with GPU runtime.
+            # Libc seems to ignore -j argument when given top-level, so `cd` into directory using
+            # the ninja flag for potentially better error messages and being more explicit about it
+            if add_check == 'check-libc':
+                ninja_test_args = [
+                    'ninja',
+                    '-C ' + llvm_builddir + '/runtimes/runtimes-bins',
+                    '-j 1'
+                    ]
+
             f.addStep(LitTestCommand(
                 name = 'Add check ' + add_check,
                 command = [ninja_test_args, add_check],