diff --git a/alloy.py b/alloy.py
index 2dc3fe44..34e3b439 100755
--- a/alloy.py
+++ b/alloy.py
@@ -730,7 +730,10 @@ def validation_run(only, only_targets, reference_branch, number, notify, update,
                 # *always* specify default values for global variables on each loop iteration
                 stability.wrapexe = ""
                 stability.compiler_exe = None
-
+                # choosing right compiler for a given target
+                # sometimes clang++ is not avaluable. if --ispc-build-compiler = gcc we will pass in g++ compiler
+                if options.ispc_build_compiler == "gcc":
+                    stability.compiler_exe = "g++"
                 if ("knc-generic" in stability.target) or ("knl-generic" in stability.target):
                     stability.compiler_exe = "icpc"
                 stability.wrapexe = get_sde() + " " + sde_targets[j][0] + " -- "
diff --git a/run_tests.py b/run_tests.py
index 2774ab4c..41705747 100755
--- a/run_tests.py
+++ b/run_tests.py
@@ -270,9 +270,12 @@ def run_test(testname):
                 elif (options.target == "knl-generic"):
                     cc_cmd = "%s -O2 -I. %s %s test_static.cpp -DTEST_SIG=%d %s -o %s" % \
                          (options.compiler_exe, gcc_arch, "-xMIC-AVX512", match, obj_name, exe_name)
-                elif (options.target == "avx512knl-i32x16"):
+                elif (options.target == "avx512knl-i32x16" and options.compiler_exe == "clang++"):
                     cc_cmd = "%s -O2 -I. %s %s test_static.cpp -DTEST_SIG=%d %s -o %s" % \
                          (options.compiler_exe, gcc_arch, "-march=knl", match, obj_name, exe_name)
+                elif (options.target == "avx512skx-i32x16" and options.compiler_exe == "clang++"):
+                    cc_cmd = "%s -O2 -I. %s %s test_static.cpp -DTEST_SIG=%d %s -o %s" % \
+                         (options.compiler_exe, gcc_arch, "-march=skx", match, obj_name, exe_name)
                 else:
                     cc_cmd = "%s -O2 -I. %s %s test_static.cpp -DTEST_SIG=%d %s -o %s" % \
                          (options.compiler_exe, gcc_arch, gcc_isa, match, obj_name, exe_name)