diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ec141198a81..099c76aee60 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2020-04-24  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/94383
+	* g++.dg/compat/struct-layout-1.exp: Use the -std=c++14 vs. -std=c++17
+	ABI compatibility testing even with ALT_CXX_UNDER_TEST, as long as
+	that compiler accepts -std=c++14 and -std=c++17 options.
+
 2020-04-24  Andrew Stubbs  <ams@codesourcery.com>
 
 	* lib/target-supports.exp (available_vector_sizes): Add amdgcn.
diff --git a/gcc/testsuite/g++.dg/compat/struct-layout-1.exp b/gcc/testsuite/g++.dg/compat/struct-layout-1.exp
index 99bfdbe2ff7..f2a20aafafd 100644
--- a/gcc/testsuite/g++.dg/compat/struct-layout-1.exp
+++ b/gcc/testsuite/g++.dg/compat/struct-layout-1.exp
@@ -142,7 +142,19 @@ if { $status == 0 } then {
     file delete -force $tstobjdir
     file mkdir $tstobjdir
     set generator_args "-s $srcdir/$subdir -d $tstobjdir"
-    if { $use_alt == 0 } then {
+    set test_cxx14_vs_cxx17 1
+    if { $use_alt != 0 } then {
+	compat-use-alt-compiler
+	if { [check_no_compiler_messages_nocache compat_alt_has_cxx14 object {
+		int dummy; } "-std=c++14"] == 0 } {
+	    set test_cxx14_vs_cxx17 0
+	} elseif { [check_no_compiler_messages_nocache compat_alt_has_cxx17 object {
+		int dummy; } "-std=c++17"] == 0 } {
+	    set test_cxx14_vs_cxx17 0
+	}
+	compat-use-tst-compiler
+    }
+    if { $test_cxx14_vs_cxx17 != 0 } then {
 	set generator_args "$generator_args -c"
     }
     if [info exists env(RUN_ALL_COMPAT_TESTS) ] then {