diff --git a/clang/test/Driver/avr-toolchain.c b/clang/test/Driver/avr-toolchain.c
--- a/clang/test/Driver/avr-toolchain.c
+++ b/clang/test/Driver/avr-toolchain.c
@@ -12,6 +12,13 @@
 // CHECK1-SAME: "-o" "a.out"
 // CHECK1-SAME: {{^}} "--gc-sections"
 
+/// Check the case where avr-libc lives at $SYSROOT/avr.
+// RUN: %clang %s -### -target avr --sysroot %S/Inputs/basic_avr_tree/usr/lib -resource-dir=%S/Inputs/resource_dir 2>&1 | FileCheck --check-prefix=CHECK2 %s
+// CHECK2: clang{{.*}} "-cc1" "-triple" "avr"
+// CHECK2-SAME: "-isysroot" "[[SYSROOT:[^"]+/basic_avr_tree/usr/lib]]"
+// CHECK2-SAME: "-internal-isystem"
+// CHECK2-SAME: {{^}} "[[SYSROOT]]/avr/include"
+
 // RUN: %clang %s -### -target avr 2>&1 | FileCheck -check-prefix=CC1 %s
 // CC1: clang{{.*}} "-cc1" "-triple" "avr" {{.*}} "-fno-use-init-array"