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
@@ -11,3 +11,7 @@
 
 // RUN: %clang %s -### -target avr --sysroot %S/Inputs/basic_avr_tree 2>&1 -nostdlibinc | FileCheck -check-prefix CC1C %s
 // CC1C-NOT: "-internal-isystem" {{".*avr/include"}}
+
+// Test that the driver finds an avr-libc installation at `$SYSROOT/avr/`.
+// RUN: %clang %s -### -no-canonical-prefixes -target avr --sysroot %S/Inputs/basic_avr_tree/usr/lib 2>&1 | FileCheck -check-prefix CC1D %s
+// CC1D: clang{{.*}} "-cc1" "-triple" "avr" {{.*}} "-internal-isystem" {{".*avr/include"}}