diff --git a/clang-tools-extra/clangd/QueryDriverDatabase.cpp b/clang-tools-extra/clangd/QueryDriverDatabase.cpp
--- a/clang-tools-extra/clangd/QueryDriverDatabase.cpp
+++ b/clang-tools-extra/clangd/QueryDriverDatabase.cpp
@@ -136,10 +136,26 @@
 }
 
 llvm::Optional<DriverInfo>
-extractSystemIncludesAndTarget(PathRef Driver, llvm::StringRef Lang,
+extractSystemIncludesAndTarget(llvm::SmallString<128> Driver,
+                               llvm::StringRef Lang,
                                llvm::ArrayRef<std::string> CommandLine,
                                const llvm::Regex &QueryDriverRegex) {
   trace::Span Tracer("Extract system includes and target");
+
+  if (!llvm::sys::path::is_absolute(Driver)) {
+    assert(llvm::none_of(
+        Driver, [](char C) { return llvm::sys::path::is_separator(C); }));
+    auto DriverProgram = llvm::sys::findProgramByName(Driver);
+    if (DriverProgram) {
+      vlog("System include extraction: driver {0} expanded to {1}", Driver,
+           *DriverProgram);
+      Driver = *DriverProgram;
+    } else {
+      elog("System include extraction: driver {0} not found in PATH", Driver);
+      return llvm::None;
+    }
+  }
+
   SPAN_ATTACH(Tracer, "driver", Driver);
   SPAN_ATTACH(Tracer, "lang", Lang);
 
@@ -332,7 +348,11 @@
     }
 
     llvm::SmallString<128> Driver(Cmd->CommandLine.front());
-    llvm::sys::fs::make_absolute(Cmd->Directory, Driver);
+    if (llvm::any_of(Driver,
+                       [](char C) { return llvm::sys::path::is_separator(C); }))
+      // Driver is a not a single executable name but instead a path (either
+      // relative or absolute).
+      llvm::sys::fs::make_absolute(Cmd->Directory, Driver);
 
     if (auto Info =
             QueriedDrivers.get(/*Key=*/(Driver + ":" + Lang).str(), [&] {
diff --git a/clang-tools-extra/clangd/test/system-include-extractor.test b/clang-tools-extra/clangd/test/system-include-extractor.test
--- a/clang-tools-extra/clangd/test/system-include-extractor.test
+++ b/clang-tools-extra/clangd/test/system-include-extractor.test
@@ -3,21 +3,24 @@
 # The mock driver below is a shell script:
 # REQUIRES: shell
 
+# Create a bin directory to store the mock-driver and add it to the path
+# RUN: mkdir -p %t.dir/bin
+# RUN: export PATH=%t.dir/bin:$PATH
 # Generate a mock-driver that will print %temp_dir%/my/dir and
 # %temp_dir%/my/dir2 as include search paths.
-# RUN: echo '#!/bin/sh' >> %t.dir/my_driver.sh
-# RUN: echo '[ "$0" = "%t.dir/my_driver.sh" ] || exit' >> %t.dir/my_driver.sh
-# RUN: echo 'args="$*"' >> %t.dir/my_driver.sh
-# RUN: echo '[ -z "${args##*"-nostdinc"*}" ] || exit' >> %t.dir/my_driver.sh
-# RUN: echo '[ -z "${args##*"-isysroot=/isysroot"*}" ] || exit' >> %t.dir/my_driver.sh
-# RUN: echo 'echo " $* " | grep " --sysroot /my/sysroot/path " || exit' >> %t.dir/my_driver.sh
-# RUN: echo 'echo line to ignore >&2' >> %t.dir/my_driver.sh
-# RUN: echo 'printf "Target: arm-linux-gnueabihf\r\n" >&2' >> %t.dir/my_driver.sh
-# RUN: echo 'printf "#include <...> search starts here:\r\n" >&2' >> %t.dir/my_driver.sh
-# RUN: echo 'echo %t.dir/my/dir/ >&2' >> %t.dir/my_driver.sh
-# RUN: echo 'echo %t.dir/my/dir2/ >&2' >> %t.dir/my_driver.sh
-# RUN: echo 'printf "End of search list.\r\n" >&2' >> %t.dir/my_driver.sh
-# RUN: chmod +x %t.dir/my_driver.sh
+# RUN: echo '#!/bin/sh' >> %t.dir/bin/my_driver.sh
+# RUN: echo '[ "$0" = "%t.dir/bin/my_driver.sh" ] || exit' >> %t.dir/bin/my_driver.sh
+# RUN: echo 'args="$*"' >> %t.dir/bin/my_driver.sh
+# RUN: echo '[ -z "${args##*"-nostdinc"*}" ] || exit' >> %t.dir/bin/my_driver.sh
+# RUN: echo '[ -z "${args##*"-isysroot=/isysroot"*}" ] || exit' >> %t.dir/bin/my_driver.sh
+# RUN: echo 'echo " $* " | grep " --sysroot /my/sysroot/path " || exit' >> %t.dir/bin/my_driver.sh
+# RUN: echo 'echo line to ignore >&2' >> %t.dir/bin/my_driver.sh
+# RUN: echo 'printf "Target: arm-linux-gnueabihf\r\n" >&2' >> %t.dir/bin/my_driver.sh
+# RUN: echo 'printf "#include <...> search starts here:\r\n" >&2' >> %t.dir/bin/my_driver.sh
+# RUN: echo 'echo %t.dir/my/dir/ >&2' >> %t.dir/bin/my_driver.sh
+# RUN: echo 'echo %t.dir/my/dir2/ >&2' >> %t.dir/bin/my_driver.sh
+# RUN: echo 'printf "End of search list.\r\n" >&2' >> %t.dir/bin/my_driver.sh
+# RUN: chmod +x %t.dir/bin/my_driver.sh
 
 # Create header files my/dir/a.h and my/dir2/b.h
 # RUN: mkdir -p %t.dir/my/dir
@@ -27,7 +30,7 @@
 
 # Generate a compile_commands.json that will query the mock driver we've
 # created. Which should add a.h and b.h into include search path.
-# RUN: echo '[{"directory": "%/t.dir", "command": "%/t.dir/my_driver.sh the-file.cpp -nostdinc --sysroot /my/sysroot/path -isysroot=/isysroot", "file": "the-file.cpp"}]' > %t.dir/compile_commands.json
+# RUN: echo '[{"directory": "%/t.dir", "command": "my_driver.sh the-file.cpp -nostdinc --sysroot /my/sysroot/path -isysroot=/isysroot", "file": "the-file.cpp"}]' > %t.dir/compile_commands.json
 
 # RUN: sed -e "s|INPUT_DIR|%/t.dir|g" %s > %t.test.1
 # On Windows, we need the URI in didOpen to look like "uri":"file:///C:/..."